Is there a way to play more than one clip from one card simultaneously on the desktop? Probably not possible, but I thought I'd ask!

No, not possible.
After fifteen years this has never been a possibility.

Might be possible with full-screen scenes. I never use full-screen so I know nothing about it.

After fifteen years this has never been a possibility.

It has happened by accident when I've built a multi-girl scene and the main and a background clip have been selected simultaneously from the same card..... but not in a usable, useful way. Shame though, would be fun.