Add new macros to default jet-woo-builder macros list and assign a callback functions.

jet-woo-builder-percentage-sale-min-max-discount-macros.php

<?php
	add_filter( 'jet-woo-builder/macros/macros-list', function( $macros ) {
		$macros['percentage_sale_max'] = 'get_percentage_sale_max';
		$macros['percentage_sale_min'] = 'get_percentage_sale_min';

		return $macros;
	} );
	
	function get_percentage_sale_max() {
		global $product;

		$percentage_sale = '';
		$precision       = 0;

		if ( 'variable' === $product->get_type() ) {
			$prices = jet_woo_builder()->macros->sort_variation_price( $product );

			if ( $prices['regular_min'] > 0 && $prices['regular_max'] > 0 ) {
				$percentage_max  = round( 100 - ( $prices['sale_min'] / $prices['regular_min'] * 100 ), $precision );
				$percentage_sale = $percentage_max;
			}
		} else {
			$regular_price = (float) $product->get_regular_price();
			$sale_price    = (float) $product->get_price();

			if ( $sale_price > 0 && $regular_price > 0 ) {
				$percentage_sale = round( 100 - ( $sale_price / $regular_price * 100 ), $precision );
			}
		}

		return $percentage_sale ? $percentage_sale . '&#37;' : '';
	}

	function get_percentage_sale_min() {
		global $product;

		$percentage_sale = '';
		$precision       = 0;

		if ( 'variable' === $product->get_type() ) {
			$prices = jet_woo_builder()->macros->sort_variation_price( $product );

			if ( $prices['regular_min'] > 0 && $prices['regular_max'] > 0 ) {
				$percentage_min  = round( 100 - ( $prices['sale_max'] / $prices['regular_max'] * 100 ), $precision );
				// Handle 0% value.
				$percentage_max  = round( 100 - ( $prices['sale_min'] / $prices['regular_min'] * 100 ), $precision );
				$percentage_sale = $percentage_min ?: $percentage_max;
			}
		} else {
			$regular_price = (float) $product->get_regular_price();
			$sale_price    = (float) $product->get_price();

			if ( $sale_price > 0 && $regular_price > 0 ) {
				$percentage_sale = round( 100 - ( $sale_price / $regular_price * 100 ), $precision );
			}
		}

		return $percentage_sale ? $percentage_sale . '&#37;' : '';
	}