Importing assets by drag and drop is inconsistent

Asset importing with drag and drop seems a bit inconsistent:

• When dragging and dropping assets from file manager to Form Editor, Text Editor, 3D Editor, Navigator and Asset Library  asset importer will open to start the import process
• When dragging and dropping e.g. to states editor, properties view and projects view, stop sign is shown and dropping is not allowed
• When dragging and dropping e.g. to connection view, timeline, left navigation bar, transition editor dropping seems to be allowed, but it will not start the import process, but gives "File Error" warning. I'm not sure if this file error warning is just a problem in my own DS build or a bug. Testing with QDS 2.2.1 snapshot, when e.g. an image file is dropped to timeline, it is opened in image viewer (but not imported to project).