Drag and drop of subclassed DesktopContainer

Can somebody explain to me why I can’t drag and drop a subclassed DesktopContainer (let’s call it TestDC) into my project?
When I do that the settings are’t shown.
If I drag and drop a DesktopContainer into my project everything is fine and the settings are shown.
Then I change the superclass of that DesktopContainer to the subclassed DesktopContainer (in this case TestDC) and now all the settings remain and I can use this subclassed DesktopContainer.
To me this isn’t how I expect subclassed DesktopContainers to work and it’s definitely making development by RAD much more complicated. :frowning: