This datapack will allow you to have each player when joining be given a ID that can be used via other datapacks

the variable it uses to store id is ad.id




You can also show this in the player list by typing the following command

/scoreboard objectives setdisplay list ad.id




A big thanks to Gnottero for allowing me to use this implementation for my data packs

here is some of his Datapacks

https://www.planetminecraft.com/data-pack/safe-tools/


https://www.planetminecraft.com/data-pack/homes-enhanced-just-another-homes-datapack/


you will also be able to find all my datapacks and creations at https://www.nbt-data.com/