This is about inserting a chain, either a new chain or reinstalling the old one, like after cleaning as in my case. The rear derailleur arm is fighting me of course because of spring tension. The chain in my case has a master link now.
Is there a tool, or something I can make, or some trick to hold the RD arm extended while I get the new chain on and the master link clipped?
A third hand would be great but that's a project for the future.