At present SplitPane has a divider location that is set to a number between 0 and 1 to indicate sharing of the SplitPane space between the left/top and right/bottom component.

It is possible to extend the API to have the divider location given in absolute pixel values. The use case is where you want one of your two SplitPane entries to have a fixed size, and the other to be resizable. In this case you want the divider to stay in a fixed location even if you resize the SplitPane.