When I planned a route EDMS - LIPB, I started with a direct line EDMS-LIPB and then inserted the waypoints by editing the magenta line on the map (finger drag and drop) and later corrected the levels in the virtual radar window also by finger drag and drop. All fine.

After letting SkyDemon create the briefing pack, I found crazy level values in the descent profile. The virtual radar remained correct.

It happens in iOS and in the windows-desktop version too.

What did I do wrong?

It isn't clear what the "crazy values" are that you're reporting, but when you plan a route by clicking consecutive waypoints on the map, SkyDemon automatically sets the level for the legs to a level that is above the MSA for that leg. If you're planning in mountainous terrain that would probably explain a level of 12600 feet. As always, you can set the level of individual legs by dragging them in virtual radar or going into the Leg Properties window; or set the level of the route as a whole from the Flight Details window.

Yes, sure, but why does it correctly use all the corrected levels from departure, climb and waypoint to waypoint en route, but from the top of descent onwards it jumps to that initially calculated max level all the way „down“ to the destination…?