Discant Key.

When I make a new score for my instrumet (Accordeon), I only want to use the Discant Key. How do I remove the line with the Bas-Key? And then when I want to supply again withe a Bas-Key Line - how can I do it?
I used to make scores i MuseScore 3, but I can't find tihis facillities in MuseScore 4
BR
Brigitta