It seems this problem is back.
After setting up Firefox Developer's Edition v70, then moving it to a different path, the following happens:
1. It loses the set Theme and reverts to the default Dark Theme.
2. Add-Ons no longer work. Some of them can be made to refunction by disabling then re-enabling them.
Is there a workaround, or do we need to wait for the next version of the Firefox Developer loader app?
The bug that you are talking about was already mentionned in https://portableapps.com/node/60496. And my workaround is this from the post "Just close and wait for 10 seconds and re-open and everything works."
Portabilizing application... 14 at the moment