Full disclaimer, it wasn't by conventional means, lol. My editor ended up being my fiance.
He didn't start as my editor though. My co-creator and I started writing the comic back in like... 2011? and I just kept bugging him for feedback. He's not formally trained in it, but he's VERY well read and has had a lot of experience writing his own stories, so I knew he'd be a good resource.
At first he didn't really think our story was anything remotely publishable and didn't put much stock in it, but over time he got to see little nuggets of good and eventually got invested enough that he just asked to be a part of the team proper. He ended up contributing a lot of the missing pieces and helped iron out what we already did have, so he's become a core member.
So unfortunately I don't know a lot of resources for other people to find editors. But, I will say that when it comes to finding team members in general (no matter the role) I've always had success asking for help in places where my fans can see. Many of my past and current team members were my watchers on DeviantART--I would post my job offer on the forum and they would get notified, then apply. A lot of times I didn't even realize they watched me or knew of my comic until later. But it kinda helped to have that base line connection because they were already invested (or at least interested) in both me and the project and wanted to help it grow. I imagine you could find writers and editors this way too, not just other visual art types.
In fact, my beta reader falls under the "dA watcher" category too. When we wrote chapter one we got like 5-7 people to beta read, her included, but she was the only one that really stuck through the years. She's writing a novel of her own and she doesn't know what's going to happen in our story at all, so her feedback is really valuable and eye opening.