.. I managed it ;) ... I had a general agreement, sockets that I drew into the plans and that had no explicit height indication in the plan were at 30 cm height. And for the other sockets, the height was indicated next to each one. However, the executing electrician was also my longtime neighbor who moved into the same apartment building as I did.
By the way, here – typically Erzgebirge – we also have the window socket for the Schwibbogen in every window. We did not even draw these sockets in separately. It was generally agreed that they would be installed on the left side inside the window recess in all apartments and be on a separate circuit per apartment, for which a timer can be set in the fuse box.