To truly minimize your workspace, you can view and edit your diagram in full-screen mode. This is also great for maximizing your space during presentations and Zoom meetings.
To enter full screen mode, click on the number showing your zoom percentage in the lower right corner of your workspace. From the pop-up control, choose Toggle Full Screen.
This removed not only the Left Panel (SmartPanel), but also the Main Toolbar. You can still edit your document using keyboard shortcuts and the right-click menu.