Fix: User can click `Note` from toolbar when note is already open

Because the toolbar remains open after clicking `Note`, the user can click `Note` again and create multiple notes, however only the first note is saved. Possible resolutions:

1. remove the `Note` from the toolbar when the user has already opened a note
2. hide the toolbar entirely when `Note` is open (actually this may be better bc the toolbar makes it look like markdown is available for notes, but it is not)

See attached recording

_{Huly®: UBERF-8523}