Hi,
Move/Rotate tool(M) don’t copy my variable.
It’s not a big deal, but when you have 20 or 40 circles, it’s more tedious. I would like to keep it in the copy, as with the Mirror tool.
See it in video.
Hi @jean-philippe2,
This isn’t what you asked, but might help.
Draw a line, not connected to your circles. Give that a length with a variable. Next draw another line, and give it an Equal constraint to your first line. Add your circles to the second line.
When you copy the constraint is copied, so you will be able to change multiple lengths by changing the variable.
Thank you Bob3DPO, that sounds very good as a trick.
However, I understand the principle but I can’t apply it.
The way I read your post it sounded more like a feature request.
I’ve tested… it’s perfect !!
Thanks a lot Bob3DPO 
Excellent!! I’m glad it worked for you!