Why does it seam I can only call Create Session in widgets?

Forgive me if I am going about this totally wrong as I’m only experienced with Unreal development from a online course I took a couple years back.
I have made a very basic test of the online system, by adding a second player and setting the number of players to 2, with Netmode set to Listen Server, which works. But now I’m trying to setup a basic in game UI to do something similar, but more manually like a real game would, and I’m a little stuck on calling Create Session.

Currently the Unreal Engine interface seams to only want to give me access to the CreateSession function inside widgets. I would like to be able to call it inside my Game Mode object (or maybe the Game Instance or Player Controller) I’m working on so I can have some of my widgets register to an event I will fire after the function completes successfully.

Is there a reason I can’t call Create Session outside a Widget? Can I change that?