Should I Wait for a Journal's Decision Before Revising Authorship?
You have been given the answer by the editor: That it doesn't matter yet.

Tell the other author of the paper that you asked, and the editor said to deal with it if/when you're asked to revise the paper.

Then move along with your life and work and wait for a reply. You absolutely shouldn't withdraw the paper for something like that when you've already been told how to handle it by the editor.