I'm trying to emulate the behaviour of Visual Studio regarding the opening of source files and the Tool windows.
Visual Studio seems to have a dock area that can be empty, but will still retain its size even when all tabs inside have been closed. I'll call it the CentralDock. You can place tabs in or around the CentralDock and even split it into multiple parts, but you cannot move the CentralDock out of the window it was created in. I'll show some screenshots.

Note the blank area in the topright, this is the CentralDock. When we open a source file it gets opened there.

When we open another source file it gets automatically placed there as a tab

We can split it, but note that we can only drag the tabs out and not the actual CentralDock

When we float another CDockArea it will take up the available space

I think this feature is somewhat related to #196 regarding the remaining open/autosizing.

I've donated €10 because I think the work you do on this library is awesome and would like to make another donation if you could consider adding this feature.