Today, the SplitPane dividers have a relative (percentage) position (between 0 and 1).
It is fine e.g. when one have a single divider at the middle of a window. When the window is resized, the divider is still at the middle.

But with several dividers, we may need an absolute position mode.
For instance, in SB, we have 2 panels (left and right) and a stage view at the middle (see attached test case).
Right and left panels have a min/max sizes, and one can grow/shrink the panels, following the min/max sizes. Fine.
But if one grow the window, we don't want the right and left panels to be resized. We need a way to enable an "absolute position mode" instead of a relative one.
Moreover, we need to be able to have an absolute positioning from either the left or right (vertical divider), top or bottom (horizontal divider).

SplitPane could have a setPositionMode() which can be ABSOLUTE_XXX/RELATIVE enum, and the get/setPosition() would return either a relative position (0..1) or an absolute one.
ABSOLUTE_XXX could be : ABSOLUTE_LEFT, ABSOLUTE_RIGHT, ABSOLUTE_TOP, ABSOLUTE_BOTTOM