I posted here:
https://www.remoteutilities.com/support/forums/forum1/2615-resolved_-remote-computer-popup-thumbnail-viewAnd I suppose there's still now way, but there's a workaround.
1. mouse over the thumbnail.
2. move mouse quickly to move *over* the advanced hint window image (if you move too slow you'll just move the advanced hint window around)
3. click the 'pin' icon in the upper right.
4. now you can resize the pinned advanced hint window image.
5. refresh image.
Not a bad workaround in a pinch.