Any updates on this?
The only update is that it won't be in Playnite 7.
Multiple play actions that track time is great, however, it would help to allow some dynamic arguments to play actions, so that custom URI (for example game://<some IP> to connect to a specific server) can be launched via Playnite.
So maybe something like Playnite.DesktopApp.exe --start "<id>" --action 1 --arguments "-some args", and then those arguments either replace or are added to the Arguments in the Play Action. Though perhaps the actions might be better named than automatically numbered.