Would it be possible to allow assignment/reassignment of technology groups, too? I was originally looking for a mod of this, and this is the closest to an 'ingame editor' that I could find.

I have no modding knowledge, and I'm dealing with an awkward incompatibility between 2 mods where a certain recipe isn't showing up because it isn't assigned a technology, and the one mod at fault hasn't been updated in half a year by now nor does it appear that the modder has been active.

Possible? Yes.
Am I going to do that right now? No.
A technology editor would most likely be a separate mod, however that's not the only way to solve your problem.

In the below command, replace "internal-recipe-name" with whatever the name of the missing recipe is (keep the quotes)
/c game.player.force.recipes["internal-recipe-name"].enabled = true
If you don't know what the internal name of the recipe is, press F4 to open the debug settings and search for something like "debug-tooltips" and enable it, then hover over the recipe to see its name.

This will disable achievements if you care, however you're playing modded so they won't count for steam anyway.

Oh, that's a lot simpler! Thank you!