public static synchronized DockingWindowManager getActiveInstance() {
		//
		// Assumption: the managers are put into the list in the order they are created.  The
		//             most recently created manager is the last shown manager, making it the
		//             most active.  Any time we change the active manager, it will be placed
		//             in the back of the list.
		//
		for (int i = instances.size() - 1; i >= 0; i--) {
			DockingWindowManager mgr = instances.get(i);
			if (mgr.root.isVisible()) {
				return mgr;
			}
		}
		return null;
	}
Returns the last active docking window manager which is visible.

@return the last active docking window manager which is visible.
Ghidra/Framework/Docking/src/main/java/docking/DockingWindowManager.java