Did a quickie search without noticing anything, so I've been thinking about solo_focus and, most honestly, group_sex/gangbang (though this could most certainly apply outside rating:e). Don't think we have a tag for when the focus of an image is a, typically smaller, number of subjects with some number of those directly around them.
While my immediate thought is "female_focus", that leaves out mixed subjects (traps and futanari are, again, immediate), as well as straight-up "male focus", which if there's a gender-neutral tag out of this could reduce a "male male_focus" redundancy.