Fix #104113

src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts

@@ -1494,7 +1494,7 @@ registerAction2(class extends NotebookCellAction {
 	}
 
 	async runWithContext(accessor: ServicesAccessor, context: INotebookCellActionContext): Promise<void> {
-		context.notebookEditor.viewModel!.notebookDocument.changeCellMetadata(context.cell.handle, { inputCollapsed: false });
+		context.notebookEditor.viewModel!.notebookDocument.changeCellMetadata(context.cell.handle, { outputCollapsed: false });
 	}
 });