I'm writing a science fiction series that utilizes many characters of differing species and cultures on many different planets. It would be extremely useful to be able to have nested groups such as: "alliance 1" which contains group such as "planet 1", "planet 2", etc. each containing groups such as "species", "cultures", "families", "religions", etc. that each contain groups e.g. "species" has subgroups "homo sapiens prime analog", "homo sapiens prime digital", "homo sapiens caleum", "homo sapiens kerigos", "canis sapiens familiaris", "homo sapiens digitalus", etc.

This is a small sample of what I'm trying to keep organized.

groups
|+--- alliances
|+---Conjuction (alliance)
|+---Atlantean (alliance)
|+---Dulacian (alliance)
|+---planets
|+---Caleum (planet)
|+---Earth (planet)
|+---Chilkotan (planet)
|+---species
|+---homo sapiens caleum (species)
|+---homo sapiens prime analog (species)
|+---homo sapiens prime digital (species)
|+---homo sapiens caleum (species)
|+---homo sapiens kerigos (species)
|+---canis sapiens familiaris (species)
|+---homo sapiens digitalus (species)
}+---religions
|+---beseri (religion)
|+---c'Latis (religion)
|+---kelmac (religion)