I never built support for right-to-left orientation into DockingFrames.
It’s a feature that I will not implement, because of the amount of time required to do so (I would estimate at least 5 full working days). Also I have very little experience in this area. Basically the entire layout would need to be mirrored? Every placement of tabs, titles, buttons, popup-menus, etc?
If you would like to create your own branch, and add support for some components, then please do so. I would be happy to assist e.g. by telling you which classes might need to be updated, or by explaining how some of the layouts are created.
If I could figure out how to have the toolbar fill completely across the window and make the icon buttons align right then I could add the icon buttons in reverse order.
But here are a few classes that would need to be updated for right-sided toolbars. It’s certainly not the complete list, but it would be a good start.
ToolbarContainerLayoutManager: update to move the entire set of toolbars to the right side (toolbar-container is the root Component for a set of toolbars)
ToolbarGridLayoutManager: update to right align toolbars that are part of the same column
DisplayerContentPane: to move all titles to the right side
ToolbarGroupTitle: moved from left to right, painting code must be updated
SpanToolbarLayoutManager?: probably needs an update too