diff --git a/frontend/src/features/workspace/WorkspaceView.tsx b/frontend/src/features/workspace/WorkspaceView.tsx
index 9668fdf..0aa8cb7 100644
--- a/frontend/src/features/workspace/WorkspaceView.tsx
+++ b/frontend/src/features/workspace/WorkspaceView.tsx
@@ -1051,25 +1051,38 @@ export const WorkspaceView: React.FC<WorkspaceViewProps> = ({
       <div className="flex flex-wrap items-center justify-between gap-2 border-b border-border pb-2">
         {/* Workspace selector tabs & left sidebar toggle */}
         <div className="flex flex-wrap items-center gap-1">
-          {subView === 'editor' && (
-            <button
-              type="button"
-              onClick={toggleSidebar}
-              className={`hidden sm:inline-flex h-8 w-8 items-center justify-center rounded-btn border transition-colors cursor-pointer ${
-                isSidebarCollapsed
-                  ? 'bg-panel border-accent text-accent'
-                  : 'bg-canvas border-border text-muted hover:text-main'
-              }`}
-              title={isSidebarCollapsed ? 'Ordnerleiste einblenden' : 'Ordnerleiste einklappen'}
-              aria-label={isSidebarCollapsed ? 'Ordnerleiste einblenden' : 'Ordnerleiste einklappen'}
-            >
-              {isSidebarCollapsed ? (
-                <PanelLeftOpen className="w-4 h-4" />
-              ) : (
-                <PanelLeftClose className="w-4 h-4" />
-              )}
-            </button>
-          )}
+          <button
+            type="button"
+            disabled={subView !== 'editor'}
+            onClick={subView === 'editor' ? toggleSidebar : undefined}
+            className={`hidden sm:inline-flex h-8 w-8 items-center justify-center rounded-btn border transition-colors ${
+              subView !== 'editor'
+                ? 'opacity-35 bg-canvas border-border text-faint cursor-not-allowed pointer-events-none'
+                : isSidebarCollapsed
+                ? 'bg-panel border-accent text-accent cursor-pointer'
+                : 'bg-canvas border-border text-muted hover:text-main cursor-pointer'
+            }`}
+            title={
+              subView !== 'editor'
+                ? 'Ordnerleiste nur im Notizen-Modus verfügbar'
+                : isSidebarCollapsed
+                ? 'Ordnerleiste einblenden'
+                : 'Ordnerleiste einklappen'
+            }
+            aria-label={
+              subView !== 'editor'
+                ? 'Ordnerleiste nur im Notizen-Modus verfügbar'
+                : isSidebarCollapsed
+                ? 'Ordnerleiste einblenden'
+                : 'Ordnerleiste einklappen'
+            }
+          >
+            {isSidebarCollapsed ? (
+              <PanelLeftOpen className="w-4 h-4" />
+            ) : (
+              <PanelLeftClose className="w-4 h-4" />
+            )}
+          </button>
 
           <button
             type="button"
@@ -1167,7 +1180,7 @@ export const WorkspaceView: React.FC<WorkspaceViewProps> = ({
         {/* LEFT MASTER SIDEBAR */}
         <aside
           className={`${
-            isSidebarCollapsed
+            subView !== 'editor' || isSidebarCollapsed
               ? 'hidden'
               : mobileShowDetail
               ? 'hidden lg:flex'
@@ -1382,7 +1395,7 @@ export const WorkspaceView: React.FC<WorkspaceViewProps> = ({
       {/* RIGHT DETAIL AREA (STRICTLY ISOLATED BY KEY) */}
       <main
         className={`${
-          mobileShowDetail ? 'flex' : isSidebarCollapsed ? 'flex' : 'hidden lg:flex'
+          subView !== 'editor' || mobileShowDetail || isSidebarCollapsed ? 'flex' : 'hidden lg:flex'
         } flex-1 flex-col min-w-0 h-full overflow-hidden bg-canvas`}
       >
         {subView === 'editor' && selectedDocId ? (