Hey guys, 
a friend and I started playing Grounded but he needed to go off... I wonder if there is a possibility to export the lobby from him as a file so I  can import it and keep playing?

Greetings Timmy

I know this is a bit late, but Windows?

In their game, have them look at the "Load Game" screen and find the file "Playthrough - XXXX" where XXXX is something like "8F94".  Exit the game.  

Using "File Explorer", navigate to:

C:\Users\{Username}\Saved Games\Grounded\

Have them zip up and send you a folder with a name like:

(ID-8C1CAF7943A20A15BCE1689BC43A8F94)(LOGOUT-SAVE)

Unzip that into your own "Saved Games\Grounded" and load the game.