What version of Adagio Receivables are you using? If it is Receivables 90A, then the 'Payment Type' should be underneath the Optional Fields and above the Credit Card information, when using the 'Receivables 90A' module and the 'AR Trans w Cust' table

If you are using GridView 9.0B (very recently released), then there is an option on the field selection screen to sort the fields into alphabetical order, making specific fields easier to find (as long as you know the field name).