I prepared a character for NG+ Runs, saved it from "My Games/Terraria" to my pc, tried a run, wanted to try again, deleted the character in game, reimported the Player folder but now my game doesnt find the character any more. Am i doing something wrong and this method doesnt work any more? I remember importing characters like this a few years ago.

It works just fine for me.

I just paste the .plr file into the terarria>players folder

Yeah there's 2 files + 1 folder per characterm and 3 files per world, but only one file for each actually stores the data. I honestly don't know what the other 2 do. Perhaps stuff like map exploration, or time played? Either way, the stuff you want to be copying is the .plr file and the .wld file, for players and worlds. The others just don't matter at all.

I'd assume the second player file is for the game backing it up, considering the extension. Just in case, y'know, like maybe if the player gets corrupted? Idk just a guess.