Thank you Marcello, but this does not solve my problem. In the old editor it was possible (even necessary) to use different menus on desktop and mobile. It seems there is no way to do this in Editor X… 
I am building a one page website. I don’t want a lightbox to appear and fill the hole screen only to move to a new anchor on the site. The other option would be a master section. But this means losing space on the site for a anchor menu and I can’t change it to disappear only on certain breakpoints (small mobile screens)…
In the old editor it was possible to set an element like a container to a fixed position. Now everything needs to be attached to a section. So it is not possible to build a menu that behaves like a small vertical menu and stays on top of everything at the same screen position when scrolling…
If anybody has an idea how to solve this I’d be very happy!