Slitherine

What are qualifiers and what do they do?
Didn't find them in the manual.

What I did, is start a game and if you look at various nations (before you actually select one) it will tell you if they have a qualifier and what it does.

For example, Rome is Aristroratic Elite. You can check your empires modifier in-game to see if you already have one.

And, yes, stuff like this needs to be in the manual.

It's a prefix to some nations, basically that's like another nation modifier, except they occupy a specific spot and alter also the name of your nation, that's partly flavor although they certainly have an in game effect.
Also there is a decision which allow you to switch this modifier, and that's the only one you can change this way.

That should really be in the manual. Its a big clickfest to go through the nations to find one that has a qualifier to find out what it does.
I have that decision to change it and the game is very unhelpful in the decision.