Can worker Aniimo be used in combat?

Assignment is exclusive. A creature is either working or it is available to you, and putting one on a job at the Home or on the farm takes it off the roster until you take it off the job. There is no shared use where a worker also fills a slot in the party.

That matters most because of how small the party is. You field four active Aniimo, and combat lets you swap between those four instantly in real time, so the four you bring are the whole of what you have in a fight. Every creature on labor duty is one fewer body in that rotation. Combat itself is real time and demanding, with dodging, positioning, stamina to watch and skills on cooldown, so the team you take in is the team you have to solve the fight with.

The farm lock reaches further than fights. Creatures assigned to farm labor cannot be used in the open world at all, and the open world is where environmental puzzles sit alongside the combat. A farmhand is not just benched from battle, it is out of play entirely while it works.

The practical read is to think of your collection in two groups from early on. Keep your combat mainstays free, and push duplicates or creatures you are not building toward work. If you assign something you actually rely on in a fight, you will notice the gap the next time you get into one.

Not settled: How freely a creature moves back and forth between labor and the active party, and whether pulling one off a job costs anything, is not settled yet.