[2022] I want to mod jobs into rooms.

There isn't mod support yet. However, you can edit the game data and texture atlas to mod in things. You should be able to add different jobs as long as the in-game mechanics don't need to be changed.

Mantic Marksmen, one of the discord members, has written this:
https://docs.google.com/document/d/1RW_jbZB4929M_PzpMqWBxTrXHF6PWvGwz74jn6b7pmY/edit

It's a WIP modding guide but it has quite a lot already. It might help you mod some things.

If you do decide to mod stuff, I'd suggest joining the discord as there is a modding channel and a few players chat about things there. Might help!

Oh! This should already be a job at the Wood Mill. You should be able to convert wood logs into coal with a furnace or fire pit. Is it not showing up under the productions window for you? And this is in beta, right?