1 axle or 2? I've envisioned a wheel lock for tandem axle trailers that would lock the 2 wheels together. I'm not creative enough to describe it well. If you Google chock-n-lock kinda like that, but I'm not sure you couldn't still drive off with one of those in place - I think it needs to be secured to the wheel itself somehow.
You can buy a "boot" like the police departments use when a vehicle has too many unpaid parking tickets.
Chaining the wheels is a good idea.
I'm surprised more contractors don't take wheels off when they leave their tool trailers on a job site over night (or more). If you are only moving it periodically, I think that is a great idea. BUT, some municipalities don't allow "immobile" vehicles to be parked in public areas - basically trying to avoid junk cars from being abandoned, so this may not be an option.
I'd at least put in a hitch lock, but those seem easy to work around (you can pull a trailer without setting it on the ball). But its cheap and easy for you to unlock when you are ready to use the trailer.
Another thought: get a trailer jack with removable handle, crank it all the way down and take the handle...depending on how heavy it is, might not be too easy to lift it onto a hitch without the jack.
Might also put a tracking device in/on the trailer (Airtag, or similar). I've thought about getting these for all my equipment, but haven't yet. Most phones will let the user know there is a tracking device nearby, but if you hide it well, it may either scare them enough to leave the trailer or be there long enough to get the location to police before they find it...
Like many things, if really really somebody wants it, they are going to take it. The game is to make it difficult enough that they don't want it that bad, right?