The new MDI system does have some improvements that have made the impossible possible now, and for that I am deeply grateful. Specifically, in order to work with "a few" open windows at a time, you used to have to manually arrange the tiling in order to get any sort of reasonable layout. And if you resized the main window, or opened up an "output" or other window that took up space, it would not adjust the MDI child windows' scrollbars...it was so bad that I used to just open up a bunch of terminal windows around SlickEdit, in order to see other files.
Now, however, the tabbed MDI windows just seem to predict what I want! It's sooo nice! If I have a couple of MDI windows tiled, they scale as the main window scales. If I open a new file, instead of blapping it (that's a technical term) on top of the other windows, it cleverly chooses the active MDI child and adds the new file as a tabbed window.
It's all just perfect. thank you thank you!