How do I run two separate clients with PIE?

I was having issues testing my main menu’s setup for creating and finding LAN games.

Initially I thought I had set some things incorrectly, and spent a day trying to debug and find the issue.

Eventually I got fed up and just packaged the project, and found that I could easily start two instances of the game that way.

Unfortunately, this is not ideal for making quick changes and testing them so I still need to figure out how to do it in editor.

Any clues on how I can run two separate clients with PIE?