Hmm, after playing around have learned the following.
Within a scrap one can use the menu to click Window, New Scrap Container, and then drag the selected files from the first Scrap to the second.
Alternately, one could do a Copy|Paste into the new scrap window.
So, what the heck am I even posting for? Hah.
But it'd be nice to have a built-in menu command (with shortcut key) to do just such a thing as a quick one-shot. Schwing.

