Setting `Support material/raft/skirt extruder` to Extruder 1 causes cooling settings for Extruder 2 to be ignored

[evilC]

Description of the bug

When I force supports to use a specific extruder, then fan settings for the other extruder are no longer observed.

Project file & How to reproduce

1. Load attached project cooling settings bug.zip
2. Slice
3. Change Legend to Fan Speed
4. Notice fan is enabled for top-most portion of print (This is printed by Extruder 2)
5. Change Print Settings > Multiple Extruders > Support material/raft/skirt extruder from 0 to 1
6. Slice
7. Fan is no longer enabled for top-most section, despite it not being the support extruder

As far as I can tell, what appears to be happening, is when you set Print Settings > Multiple Extruders > Support material/raft/skirt extruder to use extruder 2, it uses the Extruder 1 cooling settings for Extruder 2 for the whole of the print

Checklist of files included above

• [X] Project file
• [X] Screenshot

Version of PrusaSlicer

2.6.0-beta1

Operating system

Windows 10

Printer model

Snapmaker J1

[evilC]

Any motion on this? This bug is causing me MAJOR headaches. I can somewhat workaround it by applying the changes to extruder 1 that I want to take effect on extruder 2, but this has a knock-on effect in a number of ways. Not least is the highly annoying fact that you can make changes to, say, filament 1 just for this print (ie not save them but have the changes take effect for this print), but if you then switch to filament 2 (To say make more temporary changes for this print), it will not let you do so unless you save changes to filament 1