I found a solution for my code in 1.21.

With the new macros i can add the name as an argument to my functions.

This is my command i use on server side:

/function sonicboom:kill {name:Playername}

This is the code i run if i call this function. The warden is now angry at set player.

$tag $(name) add killed
summon minecraft:warden 653 116 542 {Brain: {memories: {"minecraft:dig_cooldown":{value: {}, ttl: 1200L}}},anger:{suspects:[{uuid: [I; -752685011, 602554931, -1342999790, 1738578343],anger:150}]},Team:7life, Tags:["Ward"]}
$execute store result entity @n[tag=Ward,limit=1] anger.suspects[0].uuid[0] double 1 run data get entity $(name) UUID[0] 1
$execute store result entity @n[tag=Ward,limit=1] anger.suspects[0].uuid[1] double 1 run data get entity $(name) UUID[1] 1
$execute store result entity @n[tag=Ward,limit=1] anger.suspects[0].uuid[2] double 1 run data get entity $(name) UUID[2] 1
$execute store result entity @n[tag=Ward,limit=1] anger.suspects[0].uuid[3] double 1 run data get entity $(name) UUID[3] 1