This script works to move the JPEG Sequences into a "proxy" subdirectory. I have it added as a Thunar Custom Action, so it works for the time being. ...

I feel like an environment variable would be a bit obtuse for something that could wind up being project specific (if working collaboratively), but I ...

Very nice. There was maybe just a little too much cutting towards the middle, but overall it was very well mastered and edited.

Largely Blender in the Open Source community.