I have unlinked several payments, but being a beginner I didn't delete the payments from the Make Payments screen. How do I find the ones that need to be deleted? There doesn't seem to be anything indicating if they are used or not.
If you have been reconciling all your transactions in your bank account(s) then you could use the 'Not reconciled' tab.
If you haven't been reconciling then you would need to do it the long way by going into each payment (by clicking on the individual line of the payment) and seeing whether it's linked to a bill or not.