Hi @B.kleinmanns, welcome to the Cayenne community.
Editing the tabs that you're discussing isn't possible in our current design. You can edit the Project tabs that appear in the black bar on top of the web dashboard currently however.
Can I ask what you have in mind if we had this sort of functionality? Do you want to just hide tabs you may not be using like Tracking on a non-GPS project? Were you hoping to make custom tabs of some sort?