Hi there, @kpgillan.
Nice to see you here in the Community.
Great news, you can enter using split accounts. The trick is to do this as separate line items. For example, the first line would be your liability account, and the second line would be your interest account.
However, it's always best to refer to your accountant for accounting advice to have the most knowledge on recording split accounts into a transaction.
You can check out this similar thread to review the advice given about entering split transactions: https://quickbooks.intuit.com/learn-support/en-us/other-questions/can-i-split-a-loan-payment-to-refl...
Also, check out: Enter a split transaction into the register for more details.
Please let me know if there's anything else that I could assist you with. You can always reach out to the Community or me anytime you find you need help. Take care and have a great Monday!