Hmm. So if I understand this well: Addons need registration (poser.RegisterAddon )to become part of the process loop and be warned about events.

GUI panes van be managed by Poser without being part of an Add-on.

The Python Shell addon does not have any visible callback functions set up but uses the addon system do become persistent ove Poser restarts.

Is there a wxPanel class that supports the drag-drop etc?