Don’t forget to give your firmware version (numbers found at the bottom of the global settings), because maybe this is already fixed in the beta version of the next to come v1.1 firmware.
It did work out! No idea, why the settings in the menu changed, maybe I pushed too many buttons …
If anyone else has this problem: You got two choices, tune and edit. In the tune mode you can - as expected - tune only. In the edit mode you can use the poti to edit (characters e.g.) and tune … Nice!