@Jici, you are going through a great deal of unnecessary work to track physical cash. Money is not inventory, and using inventory features, sales invoices, or anything else like that to track where it is activates all sorts of hard-coded functions in Manager. You will end up knowing less about where your money is than even with a broken spreadsheet.
Instead, create multiple cash accounts:
- Register 1 till
- Register 2 till
- Register 3 till
When you move cash from one to the other, enter an inter account transfer.
You can do this in a separate business used only to track cash. You would only activate the Cash Accounts and Inter Account Transfers tabs. Or you can do this as part of a business’ existinting accounts, which would have the benefit of allowing you to record movements to/from bank accounts, expenditures, etc.