Not sure why, but I copied that command and hit enter; once again I simply got "light blue banner" - not named 😞 I even double checked that it's exactly as you typed it. It's like the game doesn't even realize there's more after the "light_blue_banner" part.
I apologize for taking more time, but how do you give yourself a custom-named item now?
Aha 🙂 It works! Thanks lots 😃