Hi Victor,
for such a requirement - to create a loan which partially pays interests and partially capitalizes interests you should use the Product type 54A (Product category 540) - Cash Flow Transactions - Product Types in the Transaction Manager - SAP Library - these are kind of open structure, which allows you to create transactions whose structural characteristics cannot be mapped by other standard product categories (including the Product type 55A - it allows only one interest condition during certain period).
Kind regards,
Renatas