perfect! Thank you @Martin.Jirsak
Yes you are right. It only happens with the key command.
Can you please also add that it should be possible to open the Sampler Track floating window via that key command, instead of opening it in the lower zone?
Expected behavior for that key command is that it opens the VST instrument when clicking, and closing it when clicking again. The problem is that the sampler track is opened in the lower zone by default and that the lower zone stays open after closing the sampler track via the Edit VST instrument key command. That is really a workflow killer.
Thank you for your patience and help!