Use case or problem
The problem is that when live preview mode is turned on, selecting the “edit/preview” toggle allows toggles only between live preview and preview modes. So if I have the live preview option turned on, I currently cannot switch to edit mode, and can’t use live preview mode if I want to use edit mode without first restarting the vault.
Proposed solution
The availability of live preview mode could instead be an optional addition to edit and preview modes - each of which can be toggled on/off as available modes in the vault. This would mean that users can have the vault have any combination of the three modes (E+LP+P / E+P / E+LP / LP+P / E / LP / P) turned on to use in the vault (although of these, it seems like nobody would use just P mode - it might still be useful for a presentation/demo, for instance).