toggle-build-layer/control.lua:15: attempt to index field 'related_underground_belt' (a nil value)
stack traceback:
toggle-build-layer/control.lua:15: in function 'calculate_conversions'
toggle-build-layer/control.lua:26: in main chunk

Im getting this when trying to load into any game. Couldnt try the mod.
Its probably a incompatibility with one of my mods.
I will look into this further in my free time and do some binary batch toggleing in hopes of finding it and report back.
Until then heres my Modlist. It might be possible to auto import them when pasting into AppData\Roaming\Factorio\mods\mod-list.json

https://pastebin.com/s2k5wJaW

Yeah it's some mod that added a belt without a related_underground_belt. I'll make a check to ignore those if they don't have that field.

Will be fixed in the next version.

Fixed. But I couldn't test it against the mods. Let me know if it worked.

That was fast.

Now that you mention it one type of belt has been causing other issues for me. Bioluminescent Belts I believe from the Tenebris Mod has been messing with upgrade planners. I think they dont have underground versions.

Anyways this fixed it for me thanks!