@rvagg yes, this registered snap called yarn is not a blocker for your alias. So go ahead and request it.
What seems to me is that if we have a node snap that includes a yarn command, and a yarn snap that includes a node command, both snaps will have the same contents, just inverted names and aliases. So let’s work together on this 
For now, I will leave this yarn snap in edge so it’s not discoverable in the store. We can focus on testing your node+npm+yarn snap, and then figure out if we need one called yarn in stable too.
Is there something I can do to help you with your snap?