Great tip, thanks!
I was able to try it with someone else's copy of 14 and the two text merge fields I expected to slide still aren't, so I guess the background object wasn't the problem.
I could be misunderstanding how sliding works. I've attached a simple file with three fields, as an example. On the merge layout I was thinking serialnumber would always print right below address, but it doesn't seem to be doing that.
Do I have the concept wrong somehow?
Untitled.fmp12