Do you want to display apply coupon form somewhere in your site rather than in your cart? Now it is possible by using this module. This module allows you to display apply coupon and apply voucher at anywhere in your site.
Example
Use J2Store's special module positions to publish this at top or bottom of the checkout page. In this case, if you have a coupon for registered users, they can apply a discount coupon after log in at checkout.
Special module position for checkout
j2store-checkout-top j2store-checkout-bottom
You can also publish this module in your site using your template's available position.