there is a quirk where the game wont read files/folders in the steam save folder if the game didn’t “create”/“activate” them, when you renamed the char you changed that.
Try turn cloud save off in game and temp copy your char to the local save folder, see if the renamed char appears
if it does then that quirk was the issue, and can just reimport it afterwards (should you desire to have cloud function on still)
can follow pow’s instruction step by step if you’re not familiar with the manual copy paste How to - Move your saves from Steam cloud to Grim Dawn's default location. - #208 by powbam