The duration in milliseconds of the animation shown when a side panel is expanded.
Set this to 0 to disable expansion animation.
When a widget is being dragged and the distance of the mouse cursor to the shell border
is below this threshold, the respective side panel is expanded so the widget can be dropped
into that panel. Set this to -1 to disable expanding the side panel while dragging.
The ratio of the available shell size to use as initial size for the side panel.
How large the panel should be when it's expanded and empty.