I tried setting a splitter up as shown in your gifcat and the server crashed with this error message: Error while running the event handler: compoundsplitters/control.lua:245: attempt to index local 'buffer' (a nil value).
Still getting issues creating a splitter:
787.894 Error MainLoop.cpp:603: Exception at tick 29982: Error while running the event handler: compoundsplitters/control.lua:245: attempt to index local 'buffer' (a nil value)