Can we build a simple feature to allow dragging clips in the timeline display?
Well... not really, at least not "simple".
As it turns out, the GTK-framework only supports classic "drag-n-drop",
which translates into sending an action to a drag target to receive a "document".
And, even worse, dragging clips must be implemented as a UI gesture,
and as such overlaps with the other gestures for editing, trimming.
In 2017, I did an comprehensive analysis of this problem, and then
concluded to postpone it. Thus the task now would be to build a
*simplified preview*, while being aware of the danger of creating
oversimplified structures, and the danger to hamper a complete
solution for implementing UI gestures...