I think a button to show/hide the tags, sheets and notes sidebars would improve the user experience, especially for new customers.
Most other apps of this kind have a button for toggling the sidebar, and it useful for that reason: it’s universal.
Having to remember a keyboard shortcut that is application specific adds a layer of friction to a highly used action. I use a mouse with a mac mini, so no trackpad. Often I am in a mouse heavy state, and even finding the right key combination is a pain.
A simple button would cover all three bases: keyboard shortcut, trackpad gesture and mouse click.
This issue repeatedly comes up for me, and there’s quite a few similar request on here. So I have to speak out. Please consider this feature!