HubSpot has a feature called "Object Library" that provides some out of the box configurations based on common use cases. These objects are usable with process rules, but require checking a box when connecting HubSpot.
The "Object Library Enabled" option is disabled by default, and you'll need to check it in order to access these objects.
What happens after enabling them?
These objects will automatically be usable in process rules, and will appear in the object list when creating a process rule.
Why is there a checkbox?
HubSpot sends an email if an integration uses one of the object library permissions and that object isn't enabled.
This email can be confusing if you're not expecting it, because it will say "Supered now authorized to access disabled object(s)", or a similar message.
You do not need to do anything if you do receive this email.