Co-Author vs Transfer Ownership

I’ve developed several apps with underlying Google Sheets, but I want to transfer ownership of the apps and GS so there are no issues if I ever leave the organization.

I tried to transfer ownership to another account, but I don’t know what to put in for “New owner’s ID”. I’ve already added the user as a co-author and given editor rights to the GS.

What am I missing?

You’ll need to know the id of the user you want to transfer ownership to. You can find that id from the top of the this page: