I can't upload these to the workshop (because they're not supported)? Because for some reason I can't find my co-op map (link in the signiture) on this site when searching normally, so I assumed I needed to upload it to the workshop, but it's saying I can't because it's a co-op map.

Sorry, but I'm confused. Thanks in advance for any enlightenment.

No, coop maps aren't supported on the Workshop (at the moment). For now, you could upload any SP map to the workshop as a "placeholder" and link to the coop map here in the description.
I don't know why the normal search function doesn't bring up your maps.

you can just upload your coop maps here. If I use the search function on the forums (Three Companions) your map does show up.
The reason why it's not in the coop category?
Because it's in the spotlight category because your map is awesome ^_^

A shame about the workshop thing. As for my map being in the spotlight, I had no idea! I've found it now, just as well since I had an update for it.

Thanks a bunch for the responses! And I never thought people would like my co-op map so much. I feel kinda silly (and of course happy) now.