Feature description:

I'd personally prefer a tag, but it'd be nice if both slots in a Reactor could accept different items based on what was tagged/configured.

Having it apply to at least Carbon would be good imo.

Ideas for the tag's name:
Carbon Slot: carbon
Redstone Slot: stabilizer (also changes the hover label for redstone)
Uraninite Slot: fuel

Adding a section to the config to add more solid coolants would be great too. There's one for Thermo Heat Sources, so it's a bit odd there isn't one for Coolants too.

Why you think this feature should be added:

It'd make Reactors a bit better and allow more flexibility in custom modpacks.

(also, the CurseForge page doesn't have a quick link for this issue tracker. Would be nice if it was added).