Create my own drum kit

If you right click a drum staff and select Edit Drumset, you can customize your drum kit (as you probably know). Once you are done, there is a button at the bottom left of the dialog that lets you save your drum kit and a button next to it that lets you load it when you want to reuse it rather than recreating the drum set again.

edit: I don't think it automatically updates the name in the score, but that's easy enough using Staff properties.