You are correct. Site library.
There are no site libraries available. Usually, they are at the top of the generated press appearance.
If you don’t see the “Site Library” tab, it may not be activated yet.
To activate it, go to Appearance > GeneratePress.
You should see a list of add-ons.
On the list, you should find “Site Library”. Click Activate on its right side to activate the add-on.
The Site library tab should appear once you’ve successfully activated the add-on as shown here:
https://share.getcloudapp.com/geuqNdkQ
Note: If it is already activated and you can’t see any sites on the site library, refer to this documentation: https://docs.generatepress.com/article/site-library-unavailable/