"Friends Presence Support" in Custom Campaigns for 1.35

[Gatovalero]

Hello Everyone,

I was wondering if anybody knew what this meant. I have been making a wide range of maps to play with my friend in a coop setting and mostly entail a "coop campaign" type of experience. I am interested in what this means since it is pretty much impossible to have actual coop campaign as far as I understood. I have tried to get around it creatively but needless to say this sentence in the patch notes intrigued me greatly since coop support for custom campaigns would be amazing for this game. Can anybody tell me what this means?