I would like to know that payment page customization. Actually we need to hide the payment method based on Coupon code . Ex : if customer enter discount code "CODE-01" then we need to hide the Credit card payment option and show only paypal method.
Please advice, Currently I cant find the checkout template file in the theme directory .
Hiding or removing a payment gateway is not a feature available to all plans so this might not be possible to you today. It is something that can be done on the Shopify Plus plan either via the checkout template or the Script Editor. Related links below.