Provide side frame ordering

[dprutean]

As I can see now the frames can be placed North, South, East, West. In many situations I have to place frames one under the other, or on the same position. Having indexes and sub-indexes for each frame would help to position them. Check the jide docking.

[RobertBColton]

This is actually supported but I don't demonstrate it in the demo. There is an overload for dock that takes a sibling:

DockFX/src/main/java/org/dockfx/DockNode.java

Line 626 in 80c5e58

public void dock(DockPane dockPane, DockPos dockPos, Node sibling) {

I'll leave this open as a reminder to myself to add it into the demo so people can discover the feature easier.

[RobertBColton]

Forgive me if this is incorrect, and I will reopen this ticket, but I believe that #14 covers the same feature. So I am going to close this out as a duplicate. What was requested here is the ability to dock two nodes together into tabs and reorder them, which is essentially the feature #14 covers. Please follow that issue for further updates if it does get added. Thanks!