Check games that your group owns

go to https://steamcommunity.com/dev/apikey while logged into steam
put any url in the box. www.r33d.com would work.
it'll give you and string of characters and that is your api key you can use.
once you get the api key, scroll to the very bottom of the esgst settings and enter it in the box.
once setting 7.2 is enabled, you should see a new button that looks like a folder on group pages (also wl/bl pages).
the button will let you check if a certain game is owned by any of that group's members.

i hope that helps. i don't use the option myself so i'm just going off the description.