A feature to auto-hide the side bar (containing the notebook hirarchy) and the notes list may be useful.
Most of the time my workflow involves, opening Joplin, searching for a note or opening a note from the tree. This takes a few seconds, maybe a minute if I can't find my note. Then the rest of the time- 99.9% I am writing in the editors.
I would be nice if the side bars could be there when they are needed but can get out of the way and give up the valuable screen real estate for most of the time when they are not.
The ideal implementation would be something intuitive and simple like hovering the mouse over to the left side of the screen would temporarily expand the menus when they are needed. Maybe have a button that can lock (show) and unlock (hide) the screens.