MobTracker

Tag a mob, find it later.

Sneak + right click a mob with a stick to tag it. Right click again to untag.

/currentlocation 1
#1 Cow is at 214, 68, -1130 in world (86m away) 10 hp

Tag numbers are per player and start at 1, so yours stay small and nobody else touches them.

Commands

/currentlocation <number>   where it is now
/currentlocation list       all your tags
/currentlocation remove <number>
/currentlocation clear

Aliases: /cloc, /whereis

Unloaded mobs

You can only read a mob's position while it's loaded. So it remembers every sighting and refreshes them in the background. If the mob is sitting in an unloaded chunk you get the last known spot and how old it is, rather than a wrong answer:

#2 Wandering Trader last seen at -340, 71, 902 in world - 12m ago, chunk not loaded

Config

Tagging item, whether sneaking is required, tag limit per player, permission to tag, refresh interval, keep or drop the tag when the mob dies, show distance and health.

Tags live in tags.yml and survive restarts. If that file ever ends up unreadable the plugin says so and stops saving instead of overwriting it.

Paper 1.21+, tested on 26.2. No dependencies.