@bradlymathews found a temporary CSS solution here
I'm not sure if it's just me or not but my class name was different than what Bradly originally posted (he mentioned the class name changed once on him already, so it's possible I'm not as horrible w CSS as I thought lol):
body {
filter: invert(1);
}
body .editor-canvas-container {
filter: invert(1);
}
this makes the editor dark theme, but the canvas and where the webapp is placed is unaffected (so you can still see the correct theme on the webapp). again, I didn't find this, so if it helps anyone I'd suggest following the link above and giving bradlys post a like.