Since the discussion about Advanced mode for the Raid window... I've been thinking of how to add something like this for all windows. What I have in mind is to add a menu to WindowOptions, similar to the Frame And Titlebar menu, that uses a stack of pages from the calling window as its DataSource. Selecting an option shows that page and hides all the others, much like a TabbedPane does.
I think all that's needed from a UI standpoint is to add an attribute to TabbedPane... something like ModeSwitch="true".
From a programming standpoint, the open WindowSettings function would need to inspect the top level of the calling window tree for a TabbedPane with this attribute. If found, page names from that TabbedPane would be passed into WindowSettings as options for the Mode menu.
What this would give us is a saveable "Mode" setting that displays the corresponding page in the calling window and hides all others in that page stack. This also results in a Show event on the corresponding mode page, which would allow us to script layout changes on each mode change.