Trying to use variables to set nicknames with Tablisknu

[RanomPanda]

Hey there!
I've been trying to make a custom nickname command that saves across server reboots. The only way I know about doing this is through variables, which isn't really working.

command /nick <player=%player%> <string>:
    executable by: players
    permission: nick.change
    description: Sets a player's nick
    usage: /nick <player> <tag>
    trigger:
        set {nick.%argument 1%} to argument 2
        set argument 1's default nametag to argument 2
        set display name of argument 1's tab to "%{nick.%argument 1%}%"

This is my code, I'm trying to set argument one to have a default of the player. Which it doesn't seem to like. At the bottom I have both of my attempts on different lines and both of them error. Please help me figure this out I've been trying for an hour and the docs don't help.

Thanks!