I can't rearrange my menu

I am trying to rearrange the menu, using Appearance —> menu

I know how to do that just fine, but in this case the changes I make, are not making a difference on the front end.

I had found a line of code that fixed this online before, but accidentally got rid of it, and can’t find it again.

I am hoping someone knows what that was so I can put it back in and arrange my menu again.

Thanks!