Sometimes you just need to stash a quick variable on a given instance of a Pokémon. There’s probably a better way to do this (aspects?), but this was born out of a lazy, quick solution, and it seems to work so…
It saves the custom data directly onto that Pokémon’s persistent data.
PokemonProperties won’t pop up with these. If you leave the world and rejoin without quitting the game, they show up.