Single pay button option, if enabled, will make the payment button to a single PAY button, and the server will be able to choose the payment method after pressing the PAY button.
1. Menu > Setting > Main > Sales > Ordering > USE SINGLE PAY BUTTON
2. Select YES to enable the single pay button. Select No to Disable it.
Result
By default, the single pay button option is off and will look like this.
Enabling the setting will merge the pay buttons to a single pay button. The server will be able to choose the payment method after.