Can I use a credit balance on one supplier against a debt on another (their payments are made to the same parent group)?

Hello WindsorGardens, 

Welcome to the Community page, 

It is not possible to do this in QuickBooks, as you can't apply the payment from a certain supplier to a different one. However you could use a journal entry to move the credit balance over to the other supplier. You would select the journal when making the payment for the bill. If you are not sure how to do the journal we would advise you speak to an accountant who will be able to advise you on what to enter in.