Can there be a function to allow the DM to create multiple characters for their campaign but make them completely invisble to the players please?

Saves alot of time having to have them created seperately and not within the campaign. So dont have to constantly go back and forth. 

What purpose are you using these characters for, where the minimal information of a private character won't suffice?

If they're enemies, you really ought to be building them as monsters; it's how the system was designed and balanced.