Apply your own rules for order approval on the "Simple WooCommerce Order Approval" plugin

swoa_needs_approval.php

<?php

/* https://ptwooplugins.com/product/simple-woocommerce-order-approval/ */
/* Add this to you (child-)theme functions.php file, on a (mu-)plugin or with a plugin like Code Snippets https://wordpress.org/plugins/code-snippets/ */

/**
 * In this case, we'll only deal with $needs_approval being false, as we want to apply our rules only if the plugin rules didn't applied, which is the most common scenario
 *
 * @param bool $needs_approval As defined by the plugin rules.
 * @param object $cart_or_order WC_Cart or WC_Order.
 * @return bool
 */
function my_swoa_needs_approval( $needs_approval, $cart_or_order ) {
	if ( ! $needs_approval ) {
		// First of all, you will need to check if you're looking at the cart or at an order, and only then apply your logic
		if ( is_a( $cart_or_order, 'WC_Cart' ) ) {
			// We're checking a cart and can return true depending on our own rules
			if ( $whatever ) {
				return true;
			}
		} elseif ( is_a( $cart_or_order, 'WC_Order' ) ) {
			// We're checking an order and can return true depending on our own rules
			if ( $whatever ) {
				return true;
			}
		}
	}
	return $needs_approval;
}
add_filter( 'swoa_needs_approval', 'my_swoa_needs_approval', 10, 2 );

/**
 * In this case, we'll make an exception if the applied rule is 'product_on_backorder' for a specific product id, which we always want to sell without approval
 *
 * @param bool $needs_approval As defined by the plugin rules.
 * @param object $cart_or_order WC_Cart or WC_Order.
 * @param string $applied_rule The plugin applied rule.
 * @param mixed $object_id The object id the rule was applied because of.
 * @return bool
 */
function my_other_swoa_needs_approval( $needs_approval, $cart_or_order, $applied_rule, $object_id ) {
	if ( $needs_approval && $applied_rule === 'product_on_backorder' && $object_id === 1904 ) {
		return false;
	}
	return $needs_approval;
}
add_filter( 'swoa_needs_approval', 'my_other_swoa_needs_approval', 10, 4 );