There a Way to Change Your Display Name
 

See title

/showname on/off
/showname 1 <shows only first names>
/showname 2 <shows first and last names>
/showname 3 <shows first, last, and guild>
/showname 4 <shows first, last, guild, and titles>

If you mean to actually change it to something else , you can petition to have it changed by a GM/Guide.

oh you're talking in game.

lol ty, but I mean a way to change your forum display name. Some forums have this option as a one time thing etc. Like if you'd want to chance your display name after making a character in game and wanted to switch it to that after.

Nope. Make a new account if you want to try and start fresh with a new identity. I mean you already did enough on that forum account anyway lol. Thought you were quitting though?