In the Mariana Tek system, payment can only be split between an account balance and either a credit card or cash. The account balance will be used first, and then the credit card/cash will cover the remaining balance.
To split a payment, select the box to apply the account balance, then select either the credit on file, add a new credit card, or select cash to complete the remaining charge.
If you want to see the option to split payment types between multiple credit cards or cash and a credit card, please submit the idea on our Product Roadmap.