See screenshot of this piano score. I have cross-staff beaming in use, and the music is entered into the top stave.
m89 is correct. But in m90 the music jumps down an octave, so I want BOTH staves to switch to bass clef. I was able to switch the top stave to bass clef (that’s normal and straightforward) however I can’t switch the bottom stave to bass clef, because (technically) it has no music in it. It’s just borrowing from the top stave. No matter what I do, I can’t get the caret into the bottom stave in order to tell it to switch to bass clef.
Enter the notes in bar 89 (including the cross-staff notes).
Select all the notes in both staves in bar 89 and press R to repeat the selection into bar 90.
Lower the notes in bar 90 by an octave.
Double-click at the start of the upper staff in bar 90, press shift-C (for clef) and F (for bass clef), then Enter.
With the caret still in the upper staff at the start of bar 90, press the down-arrow key. This will move the caret into the lower staff.
Press shift-C, F, Enter.
To expand on what I mentioned in my post a little further up the page:
If you cannot insert the caret at the desired location, insert it somewhere nearby and then use the arrow keys to move it to another location - up or down to move onto another staff in the same system, or left and right to move into another rhythmic position in the same staff.
When it is where you want it, use the Clef popover.
This procedure might not be exactly what you are asking for, but it works.