Replace coupon form with a pop-up link

// Hide Coupon Form On Checkout
add_action( 'init', function() {
 
    remove_action(
        'woocommerce_before_checkout_form',
        'woocommerce_checkout_coupon_form', 10
    );
 
} );

// Show Link On Cart And Checkout
add_action(
	'woocommerce_cart_totals_after_order_total',
	'ccom_coupon_modal_trigger'
);
add_action(
	'woocommerce_before_checkout_form',
	'ccom_coupon_modal_trigger'
);

// Modal Trigger HTML And JavaScript
function ccom_coupon_modal_trigger() {

	?>
	<p style="text-align:center;">
		<a href="#" id="ccom_coupon_modal">
			Have a coupon? Click to apply.
		</a>
	</p>
	<?php

	add_action( 'wp_print_footer_scripts', function() {
		?>
		<script type="text/javascript">
		document.addEventListener( 'DOMContentLoaded', function() { 

			document.getElementById( 'ccom_coupon_modal' )
				.addEventListener( 'click', function( event ) {

				event.preventDefault();

				let coupon_code = prompt(
					'If you have a coupon code, please apply it below.'
				);

				if( coupon_code ) {
					window.location.href = '<?php echo wc_get_cart_url(); ?>?coupon_code='
						+ coupon_code;
				}

			} );

		} );
		</script>
		<?php
	} );

}