Problem with automatic crediting against sales invoice

I’ve moved your post to a new topic, because it has nothing to do with release of theme options.

Your sales invoice was automatically credited because the customer (Walk In Sale, in this case) had a negative balance in Accounts receivable. That should never have happened for a walk-in customer, indicating that you have entered other transactions incorrectly.

Sales invoices have no interaction with cash accounts. They only debit Accounts receivable for the customer specified. A separate Receive money transaction must be recorded when the invoice is paid to credit Accounts receivable and debit a cash account.

I recommend reading and understanding these two Guides:

https://forum.manager.io/t/cash-sales-selling-without-sales-invoices/7321

https://forum.manager.io/t/creating-sales-invoices/7178

And please, stop hijacking topics for unrelated questions.