Colombia Humana

No need to apologize. It seems an oversight that the guide doesn't mention the limitation, or consider all the possible scenarios and provide solutions for each.
Primary membergroup only Secondary membergroup only In group(s) and also not in group(s) In any group, regardless if primary or secondary @Jordan Invision who will either be sick of me or get a raise or both.

See the solution in this comment in reply to that guide (inGroup):
 

As an untested example, while I fully pay attention in the first droning Zoom meeting of the day:
{{if \IPS\Member::loggedIn()->inGroup(4,5)}} Members with secondary or primary group IDs of 4 and/or 5 are cooler than all the other members. Pass it on. {{endif}}  

@Makoto I wonder how is it possible to create something like Categories for Tags, and display them as such in the front-end. I don't think this plugin does that.

Yes sure; just wanted to provide another log triggered from somewhere else ;)