I just discovered the “Pickup Bahavior”.”Active”-property works well in design mode. However there is no way to access its screenplay commands.
For activation/deactivation of the pickup item itself it is the other way round:
We have no “Active”-Property for that in design mode but can access this property using screenplay.
There is some other strange behavor I noticed:
If you disable the pickup behavior of a custom pickup item in design mode and restart the game the item changes its appearance back to a health potion.