Difficult to figure it's possible to drop clip onto separator
Previously it was possible to drop a clip on a horizontal separator between two adjacent layers to create a new layer and place the dragged clip on it. As it was easy to do this by mistake, we now require the user to hover the separator for one second to be able to drop the clip, and the separator is highlighted after the hover is done.
We could experiment with an animated highlight, which starts when the mouse cursor is over the separator. The animation could maybe start after a short delay (a fraction of the one second mentioned above) to avoid flickering when dragging the clip to a different layer above/below.