In the CK there is a tab to make factions with a check box to toggle it "hidden from PC".

I assume this means un-checking the box will make it "show".... but where will this show in the game?

BBD would know more,

but just to speculate, it may have something to do with interactions between NPC's and maybe affect relationships. I've never seen faction rank in my game before, but doesn't mean if you hide it, it won't do something funny