Question

I cannot notate below a low F below the bass clef, as the notes are gray.  This is extremely annoying.  Why?

I asked this question more than a year ago when trying out Notion 5, moving to Notion 6.

Eg., A bassoon can play beyond a low F, down to a low Bb, but cannot notate this unless I manually move the note.

Answer 1

This is just the default boundary of the staff - to increase the boundary just insert a note first and drag it up/down (as you note above). You can then enter notes in that system anywhere in that new boundary.
This is set up like this, as otherwise Notion would not know whether you are entering a very low note for one instrument, or a very high note for the instrument below.
-Chris