Me and my friend are interested in running Canonless Co-Op and it would be cool to have a leaderboard for it.

You should do the actual run first. I think it'll be added to the category extensions board just like 100% multiplayer so no worries there.

For it to be added as a category there HAS to be a run of it so do it first and then it’ll be added. (And even if it doesn’t get added you can still run it)