Check out this thread from a few years back. Sounds like it has the basics of “throwing” a list and then “grabbing” it to stop it (at least on a touchscreen device.)
Instead of using the momentum factor in the Drag Dropped event, you could move the list all the way to the boundaries. You can use the [[DragX]] property to test which direction the menu is being dragged. So you would have two basic conditional cases (adjusting for your widget name and timing):
IF [[DragX]] is greater than 1 Move MyMenu to (0, [[Target.y]]) Linear 1000ms
ELSE Move MyMenu to ([[This.width-Target.width]], [[Target.y]]) Linear 1000ms.