Remove Variable Pricing section at checkout if a valid discount code is passed in via the URL.

my_pmpro_remove_variable_pricing_if_discount_code_applied.php

<?php
/**
 * Remove Variable Pricing section at checkout if a valid discount code is passed
 * in via the URL.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_remove_variable_pricing_if_discount_code_applied() {
	global $pmpro_level;
	if ( isset( $pmpro_level->code_id ) ) {
		remove_action( 'pmpro_checkout_boxes', 'pmprovp_pmpro_checkout_after_level_cost', 5 );
	}
}
add_action( 'pmpro_checkout_boxes', 'my_pmpro_remove_variable_pricing_if_discount_code_applied', 4 );