A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Hi Marc,
There isn’t a site collection in SharePoint Online called Group Site Collection. If you are referring to the Office 365 Group file site as below, then, I’d like to explain that this site is different from our SharePoint default sites and it’s not feasible to add an app and a content type to it. Thanks for your understanding.
If you are referring to the team site created for the Office 365 Group as below (which we just start rolling out to first release users), please try the steps below to check the outcome:
To create a new app:
1.Click Site Contents> New> App.
2.Choose the SharePoint site apps you want to add to this team site.
To manage site content types:
1.Click Setting Gear> Site Settings> Site Content Types.
2.Follow the steps in this article to create or customize site content types: Create or customize a site content type.
Regards,
Fraser