I’d run other software in a maximized vm window and hide it entirely when required. Try escape that. More abstractly, when parties cannot negotiate, you should

I’d run other software in a maximized vm window and hide it entirely when required. Try escape that. More abstractly, when parties cannot negotiate, you should set up a supervisor for them. On linux/x11 it would be a custom wm script which knows the priority of window classes and stacks them accordingly, regardless of their requests. Windows wm delegates geometry to apps and by that creates the whole issue. There should be a webext-exclusive API for placing items above the top layer. Together with a priority in extension settings.