How to create a treaty in a scenario?

Hi. Just trying to set up an AI vs player scenario to play with friends but I have no idea how to make a treaty in the scenario editor. In age 2 you could just set a treaty in the multiplayer lobby, but here there is a treaty editor in the scenario editor that makes no sense to me. For reference, I am trying to make a 2v6 or 3v5 scenario where there is peace for 30-40 minutes. Any advice would be appreciated!