The new burnt fuel support works and the GUI looks good. I found some bugs while I was testing it.

After a drone leaves a refueler mooring, it remains connected to the refueler mooring. To see this happen, set up a single cargo drone, refueler, provider, and requester, with supply to the refueler and provider and demand at the requester. Allow the cargo drone to refuel. After the drone leaves the refueler, remove some fuel from its inventory. The inserter at the refueler mooring will insert fuel even though the drone is not moored.

Some features do not work in the map editor. After a mooring is placed while the game is paused in the map editor, it can't be connected to circuits. When the game is unpaused in the map editor, moorings appear as proxy containers and the custom GUIs do not work.

The editor issue should now be fixed in 1.4.1

Hmm... So far I've not been able to reproduce the Refueler mooring staying connected to the drone. I'll keep looking but I might return with questions if I don't find anything

In the same vein, I've now noticed that GUI elements do not update properly when changing them while the game is paused. Will fix that tomorrow

I've been failing to repro moorings remaining connected to the drone for a bit now, and I don't see anything obvious in the code
So some more questions:
- Did it happen in editor mode?
- What fuel did you use?
- Was it a fresh save or one from previous versions of this mod?

It happened in editor mode, using version 1.4.0. I used rocket fuel. It still happens in that saved file, but I can't reproduce it in a new file anymore.

I get the feeling it might have been a side effect from the editor bug you reported. Because it wasn't that the GUI was broken, but that there's a hidden proxy container added in 1.4.0 that's visible in editor mode, which took precedence when interacting. And fiddling with it might have caused the first issue (Like the proxy container got unlinked from the mooring somehow, making it always point at the drone)

I have some workable info again, but could I possibly ask for the affected save file as well?