Yeah, this may be a workaround. Thanks.
Dear Patrick, Steven and QuanNguyen, thank you for your time and effort. All the best...

I found a solution for you : you can change GRIPS = 1 as Steve show you.

And when you want use the median of edge, deactivate the snap with the man who run (1)
and choose the snapping to the median point (2) :

Thank you for your suggestion Patrick. I will try it.