Drag and drop in Layers is difficult to drop into bottom position

Overview

When a component with a slot is in the bottom position of a Region it is tricky to drag and drop component below that component and not into the slot inside it.

Proposed resolution

There is no "space" under the final slot for the component to be dropped into. If we don't want to add un-even spacing between components (which would look bad aesthetically) perhaps negative margins could be used to tweak the size of the drop target.

User interface changes