diff --git a/frontend/src/controls_panel.rs b/frontend/src/controls_panel.rs
index d55e722..90f9cce 100644
--- a/frontend/src/controls_panel.rs
+++ b/frontend/src/controls_panel.rs
@@ -3,6 +3,7 @@ use std::cell::Cell;
 use std::mem;
 use std::ops::Not;
 use std::rc::Rc;
+use std::sync::Arc;
 use wellen::GetItem;
 use zoon::*;
 
@@ -32,7 +33,7 @@ struct ScopeForUI {
 #[derive(Clone)]
 pub struct ControlsPanel {
     selected_scope_ref: Mutable<Option<wellen::ScopeRef>>,
-    hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+    hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
     selected_var_refs: MutableVec<wellen::VarRef>,
     layout: Mutable<Layout>,
     loaded_filename: Mutable<Option<Filename>>,
@@ -40,7 +41,7 @@ pub struct ControlsPanel {
 
 impl ControlsPanel {
     pub fn new(
-        hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+        hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
         selected_var_refs: MutableVec<wellen::VarRef>,
         layout: Mutable<Layout>,
         loaded_filename: Mutable<Option<Filename>>,
@@ -114,7 +115,7 @@ impl ControlsPanel {
             ))
     }
 
-    fn scopes_panel(&self, hierarchy: Rc<wellen::Hierarchy>) -> impl Element {
+    fn scopes_panel(&self, hierarchy: Arc<wellen::Hierarchy>) -> impl Element {
         Column::new()
             .s(Height::fill())
             .s(Scrollbars::y_and_clip_x())
@@ -129,7 +130,7 @@ impl ControlsPanel {
             .item(self.scopes_list(hierarchy))
     }
 
-    fn scopes_list(&self, hierarchy: Rc<wellen::Hierarchy>) -> impl Element {
+    fn scopes_list(&self, hierarchy: Arc<wellen::Hierarchy>) -> impl Element {
         let layout = self.layout.clone();
         let mut scopes_for_ui = Vec::new();
         let mut max_level_index: usize = 0;
@@ -379,7 +380,7 @@ impl ControlsPanel {
             .label(scope_for_ui.name)
     }
 
-    fn vars_panel(&self, hierarchy: Rc<wellen::Hierarchy>) -> impl Element {
+    fn vars_panel(&self, hierarchy: Arc<wellen::Hierarchy>) -> impl Element {
         let selected_scope_ref = self.selected_scope_ref.clone();
         Column::new()
             .s(Align::new().top())
@@ -401,7 +402,7 @@ impl ControlsPanel {
     fn vars_list(
         &self,
         selected_scope_ref: wellen::ScopeRef,
-        hierarchy: Rc<wellen::Hierarchy>,
+        hierarchy: Arc<wellen::Hierarchy>,
     ) -> impl Element {
         let vars_for_ui = hierarchy
             .get(selected_scope_ref)
diff --git a/frontend/src/header_panel.rs b/frontend/src/header_panel.rs
index d12c60e..7f97895 100644
--- a/frontend/src/header_panel.rs
+++ b/frontend/src/header_panel.rs
@@ -1,16 +1,16 @@
 use crate::{platform, script_bridge, Filename, Layout};
-use std::rc::Rc;
+use std::sync::Arc;
 use zoon::*;
 
 pub struct HeaderPanel {
-    hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+    hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
     layout: Mutable<Layout>,
     loaded_filename: Mutable<Option<Filename>>,
 }
 
 impl HeaderPanel {
     pub fn new(
-        hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+        hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
         layout: Mutable<Layout>,
         loaded_filename: Mutable<Option<Filename>>,
     ) -> impl Element {
@@ -68,7 +68,7 @@ impl HeaderPanel {
                 Task::start(async move {
                     if let Some(filename) = platform::pick_and_load_waveform(None).await {
                         loaded_filename.set_neq(Some(filename));
-                        hierarchy.set(Some(Rc::new(platform::get_hierarchy().await)))
+                        hierarchy.set(Some(Arc::new(platform::get_hierarchy().await)))
                     }
                 })
             })
@@ -267,22 +267,30 @@ impl HeaderPanel {
                 .family([FontFamily::new("Courier New"), FontFamily::Monospace]))
             .s(Scrollbars::both())
             .s(Height::default().max(100))
-            .child_signal(command_result.signal_ref(|result| match result {
-                Some(Ok(js_value)) => {
-                    if let Some(string_value) = js_value.as_string() {
-                        string_value
-                    } else if let Some(number_value) = js_value.as_f64() {
-                        number_value.to_string()
-                    } else if let Some(bool_value) = js_value.as_bool() {
-                        bool_value.to_string()
-                    } else {
-                        format!("{js_value:?}")
+            .child_signal(command_result.signal_ref(|result| {
+                fn format_complex_js_value(js_value: &JsValue) -> String {
+                    let value = format!("{js_value:?}");
+                    let value = value.strip_prefix("JsValue(").unwrap_throw();
+                    let value = value.strip_suffix(')').unwrap_throw();
+                    value.to_owned()
+                }
+                match result {
+                    Some(Ok(js_value)) => {
+                        if let Some(string_value) = js_value.as_string() {
+                            string_value
+                        } else if let Some(number_value) = js_value.as_f64() {
+                            number_value.to_string()
+                        } else if let Some(bool_value) = js_value.as_bool() {
+                            bool_value.to_string()
+                        } else {
+                            format_complex_js_value(js_value)
+                        }
                     }
+                    Some(Err(js_value)) => {
+                        format!("ERROR: {}", format_complex_js_value(js_value))
+                    }
+                    None => "-".to_owned(),
                 }
-                Some(Err(js_value)) => {
-                    format!("Error: {js_value:?}")
-                }
-                None => "-".to_owned(),
             }))
     }
 }
diff --git a/frontend/src/main.rs b/frontend/src/main.rs
index a783db7..a54a5e9 100644
--- a/frontend/src/main.rs
+++ b/frontend/src/main.rs
@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::sync::Arc;
 use zoon::*;
 
 mod platform;
@@ -25,6 +25,7 @@ type Filename = String;
 #[derive(Default)]
 struct Store {
     selected_var_refs: MutableVec<wellen::VarRef>,
+    hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
 }
 
 static STORE: Lazy<Store> = lazy::default();
@@ -39,7 +40,7 @@ fn main() {
 }
 
 fn root() -> impl Element {
-    let hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>> = <_>::default();
+    let hierarchy = STORE.hierarchy.clone();
     let selected_var_refs = STORE.selected_var_refs.clone();
     let layout: Mutable<Layout> = <_>::default();
     let loaded_filename: Mutable<Option<Filename>> = <_>::default();
diff --git a/frontend/src/script_bridge.rs b/frontend/src/script_bridge.rs
index 31d66bc..139e2f2 100644
--- a/frontend/src/script_bridge.rs
+++ b/frontend/src/script_bridge.rs
@@ -1,6 +1,9 @@
 use crate::STORE;
+use wellen::GetItem;
 use zoon::*;
 
+type FullVarName = String;
+
 #[wasm_bindgen(
     inline_js = r#"export function strict_eval(code) { "use strict"; return eval?.(`${code}`) }"#
 )]
@@ -14,14 +17,53 @@ pub struct FW;
 
 #[wasm_bindgen]
 impl FW {
+    /// JS: `FW.say_hello()` -> `Hello!`
     pub fn say_hello() -> String {
         "Hello!".to_owned()
     }
 
-    pub fn clear_variables() -> String {
+    /// JS: `FW.clear_selected_vars()` -> `4`
+    pub fn clear_selected_vars() -> usize {
         let mut vars = STORE.selected_var_refs.lock_mut();
         let var_count = vars.len();
         vars.clear();
-        format!("{var_count} variables cleared")
+        var_count
+    }
+
+    /// JS: `FW.select_vars(["simple_tb.s.A", "simple_tb.s.B"])` -> `2`
+    pub fn select_vars(full_var_names: Vec<FullVarName>) -> usize {
+        if let Some(hierarchy) = STORE.hierarchy.get_cloned() {
+            let mut new_var_refs = Vec::new();
+            for full_var_name in full_var_names {
+                let path_with_name = full_var_name.split_terminator('.').collect::<Vec<_>>();
+                if let Some((name, path)) = path_with_name.split_last() {
+                    if let Some(var_ref) = hierarchy.lookup_var(path, name) {
+                        new_var_refs.push(var_ref);
+                    }
+                }
+            }
+            let var_ref_count = new_var_refs.len();
+            STORE.selected_var_refs.lock_mut().replace(new_var_refs);
+            return var_ref_count;
+        }
+        0
+    }
+
+    pub fn loaded_filename() -> String {
+        format!("todo loaded filename")
+    }
+
+    /// JS: `FW.selected_vars()` -> `["simple_tb.s.A", "simple_tb.s.B"]`
+    pub fn selected_vars() -> Vec<FullVarName> {
+        if let Some(hierarchy) = STORE.hierarchy.get_cloned() {
+            let mut full_var_names = Vec::new();
+            for var_ref in STORE.selected_var_refs.lock_ref().as_slice() {
+                let var = hierarchy.get(*var_ref);
+                let var_name = var.full_name(&hierarchy);
+                full_var_names.push(var_name);
+            }
+            return full_var_names;
+        }
+        Vec::new()
     }
 }
diff --git a/frontend/src/waveform_panel.rs b/frontend/src/waveform_panel.rs
index 2493ea9..09d5f84 100644
--- a/frontend/src/waveform_panel.rs
+++ b/frontend/src/waveform_panel.rs
@@ -1,5 +1,5 @@
 use crate::platform;
-use std::rc::Rc;
+use std::sync::Arc;
 use wellen::GetItem;
 use zoon::*;
 
@@ -12,13 +12,13 @@ const ROW_GAP: u32 = 4;
 #[derive(Clone)]
 pub struct WaveformPanel {
     selected_var_refs: MutableVec<wellen::VarRef>,
-    hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+    hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
     canvas_controller: Mutable<ReadOnlyMutable<Option<PixiController>>>,
 }
 
 impl WaveformPanel {
     pub fn new(
-        hierarchy: Mutable<Option<Rc<wellen::Hierarchy>>>,
+        hierarchy: Mutable<Option<Arc<wellen::Hierarchy>>>,
         selected_var_refs: MutableVec<wellen::VarRef>,
     ) -> impl Element {
         Self {
@@ -111,7 +111,7 @@ impl WaveformPanel {
 
     async fn push_var(
         controller: &PixiController,
-        hierarchy: &Mutable<Option<Rc<wellen::Hierarchy>>>,
+        hierarchy: &Mutable<Option<Arc<wellen::Hierarchy>>>,
         var_ref: wellen::VarRef,
     ) {
         let hierarchy = hierarchy.get_cloned().unwrap();
diff --git a/frontend/typescript/bundles/pixi_canvas.js b/frontend/typescript/bundles/pixi_canvas.js
index d542b5e..674bb70 100644
--- a/frontend/typescript/bundles/pixi_canvas.js
+++ b/frontend/typescript/bundles/pixi_canvas.js
@@ -35316,10 +35316,12 @@ var VarSignalRow = class {
     this.draw();
   }
   draw() {
-    if (this.app === null || this.app.screen === null) {
+    if (this?.app?.screen?.width === void 0) {
       return;
     }
-    this.row_container_background.width = this.app.screen.width;
+    if (this?.row_container_background?._texture?.orig?.width !== void 0) {
+      this.row_container_background.width = this.app.screen.width;
+    }
     this.signal_blocks_container.removeChildren();
     this.timeline.blocks.forEach((timeline_block) => {
       const signal_block = new Container();
diff --git a/frontend/typescript/pixi_canvas/pixi_canvas.ts b/frontend/typescript/pixi_canvas/pixi_canvas.ts
index 04e0935..39b896d 100644
--- a/frontend/typescript/pixi_canvas/pixi_canvas.ts
+++ b/frontend/typescript/pixi_canvas/pixi_canvas.ts
@@ -275,12 +275,14 @@ class VarSignalRow {
 
     draw() {
         // Screen can be null when we are, for instance, switching between miller columns and tree layout
-        // and then the canvas has to be recreated
-        if (this.app === null || this.app.screen === null) {
+        // and then the canvas has to be recreated.
+        if (this?.app?.screen?.width === undefined) {
             return;
         }
-
-        this.row_container_background.width = this.app.screen.width;
+        // Workaround for "TypeError: Cannot read properties of null (reading 'orig')"
+        if (this?.row_container_background?._texture?.orig?.width !== undefined) {
+            this.row_container_background.width = this.app.screen.width;
+        }
 
         // @TODO optimize by reusing a pool of blocks instead or removing all children on every redraw?
         this.signal_blocks_container.removeChildren();