First I want to mention, that I personally found this method today, and if Gameflip moderators see this, please don’t fix.
So, you came here to change your Rocket League listing title, and the method of doing it is inspecting the name of the item after you made a listing and then it will show you
So the only thing you want to do is change the disabled keyword and delete it!
After you deleted it, go and change your listing name and press list.
And there you go! you have changed your Rocket League listing title to what ever you wanted!