Transfer "out of" or "into" budget book

Also would be useful to be able to transfer “into” or “out” of the budget books (if you have no budget book of the source/recipient). Example would be if my wife does not use the app and just maintains an excel file of our shared house budget. So I transfer a certain amount monthly to our shared bank account, but I suppose it is not an expense, but you can only transfer from one account to another, so perhaps a work around is I can create an account that is named “shared bank account.” But really, I want to put all of our transactions here in the app, but transferring between budget books is currently not available.