Sorry, I don’t know the English name.
If i use a Studierzeichen, I would sometimes rather type in own letters, like V, CH, BR (Verse, Chorus, Bridge) istead of A,B,C.
Is there way to edit “Studierzeichen”

Best Regards

No, you can’t change the text in rehearsal marks to any old text you choose, I’m afraid. In the near future you will be able to create bordered text objects that will allow you to produce items that look like rehearsal marks but use text of your own choosing.