There's a new portal in every single adventure.
I'm leaning on the idea (fictional anchor?) that the purpose for Sadie Cat and Mao as designated do gooders is to travel from one honeycomb portal to another in each universe they travel to, helping the individuals they run into along the way. As they do this, their "good will" connects the portals together, ultimately connecting all of the portals across all of the universes together via good.
This is their mission.