Convert the app to use an off-canvas split view. This was popular on the iPad Facebook app and was also available on the iPhone app. The benefit is that the menu can remain offscreen until called on by the user. The method used to request the menu to appear is often a menu (or hamburger) icon (three horizontal lines stacked one on top of the other) as well as a left-to-right swipe near the left edge of the screen.

Modify the existing split view app so that the user can hide the sidebar in order to gain more space to work with their note. This is often done with a toggle button in the navigation bar.

Try moving the sidebar to the right-hand side of the screen instead of the left-hand side.

Add a second sidebar on the right-hand side that appears when the user requests it. (This is also seen in the iPad Facebook app as the chat sidebar.)