I would think folks using it would prefer a one step activation. Would a translucent button to collapse/expand it in the same location work? The button could have 'TB' on it for ID-ing. 
The side panel sounds good.
Edit- Maybe a 'minus' in the tool bar like on a browser?
The side panel sounds good.
Edit- Maybe a 'minus' in the tool bar like on a browser?
Dell Latitude 13.5" 2-in-1 Ubuntu/Win 11
Samsung Note Pro SM-P900 12.2 Android 5.0.2
Samsung S7+, Android 12
Samsung Note Pro SM-P900 12.2 Android 5.0.2
Samsung S7+, Android 12