MDI vs SDI
Peter T: thanks for the reasoned dialog. I live in Excel 365 but keep 2010 around for those older apps that need to display n sheets concurrently in a single window, or stack them in one window and rapidly switch back and forth under user (button) or program control. That's what prompted my original post. Dreaming to simplify with only one interface that does both things equally well (MDI). Guess we've beat this one to silence.

Agree to disagree on the difficulty of MS programming excel platform between MDI & SDI.
Pete A