I found various topics on this on the Web, but none that really solved my problem.
The issue has been reported several time :
When you create a via in Eagle, you cannot get rid of it in a simple manner.
Eagle will provide you this stupid message :
"Can't backannotate this operation. Please do this in the schematics !"
But there is nothing related in the schematics. Looking in various posts on the web, you learn that you
need to use the ripup tool. But it does not work !
Ripup removes the via (with half of the work you already did), but leaves the hole in the "20 (dimension)" Layer.
I found no way to remove this hole. Please HELP !