The feature definitely is part of the Portal Engine setup, I have clients using it in v11 without issue. The users I tested against were also Editor privilege levels with CMS Editor role assigned. I don't believe this role is part of the base v12 install any longer so maybe you're missing some permissions on the Content module for the editor role you have. If you go to Roles > select the editor's role > Permissions, then select the Content module. The only ones I have unchecked are:
- Check in any page
- Modify permissions
Global Admin privilege level, doesn't follow the role restrictions so hard to do testing with that. What you might do is clone the editor's role in question, create a new user and assign it that new role you cloned, then start adding/removing permissions to it while checking access in a private window.
If you can't get it working, I'd suggest contacting firstname.lastname@example.org as this should be available to your editors.