[Feature Request] In Editor, allow user to drag-n-drop frames with mouse

[raindropsfromsky]

Is your feature request related to a problem? Please describe.
It is very laborious to edit the frames by clicking on the Move Left and Move Right buttons.

Describe the solution you'd like

1. Allow user to drag-n-drop the selection (multiple frames) with a simple drag-n-drop operation.
2. While dragging, show the insertion point wqith a line between frames.
3. Allow the user to drop the selection before the starting frame.
   (Currently this is not allowed.)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.