Umamusume - extra characters tags

Since extra tags is deprecated, is there other way to tags umamusume extra characters? Artists usual draw the extra characters in many difference physical characteristics (ex post #6652184) so we can't tags them as other mobs game characters like justice task force member (blue archive) expect if the character is from game ( ex post #5947456)

That character already has a chartag. For official unnamed characters from the game, you can tag them based on unique visual traits, like npc with flower ornament (umamusume) or grey-haired horse girl (umamusume) and so on. If they're an artist's OC you can use the artist's name as a qualifier.

These tag names don't have to be perfect or permanent, they just have to be unique.