Multi-currency for GF: show the currency dropdown as a button group.

functions.php

<?php
/**
 * Multi-currency for GF: show the currency dropdown as a button group.
 *
 * Requires: Gravity Forms + Multi-currency for Gravity Forms.
 * Paste into Code Snippets (run everywhere) or your theme functions.php.
 */
add_action( 'wp_enqueue_scripts', 'idea_mcg_currency_switcher_button_group_assets', 20 );
function idea_mcg_currency_switcher_button_group_assets() {
	if ( is_admin() ) {
		return;
	}
	$css = '
		.ginput_container_multicurrency .mcg-currency-select-hidden {
			position: absolute !important;
			width: 1px !important;
			height: 1px !important;
			padding: 0 !important;
			margin: -1px !important;
			overflow: hidden !important;
			clip: rect(0, 0, 0, 0) !important;
			white-space: nowrap !important;
			border: 0 !important;
		}
		.mcg-currency-button-group {
			display: flex;
			flex-wrap: wrap;
		}
		.mcg-currency-button-group .mcg-currency-btn {
			cursor: pointer;
			padding: 0.5rem 1rem;
			border: 1px solid #ccc;
			border-radius: 0 !important;
			background: #fff !important;
			font: inherit;
			line-height: 1.2;
			color: #000 !important;
			outline: none !important;
		}
		.mcg-currency-button-group .mcg-currency-btn:focus {
			outline: none !important;
		}
		.mcg-currency-button-group .mcg-currency-btn:hover {
			border-color: #666;
		}
		.mcg-currency-button-group .mcg-currency-btn.is-active {
			background: #2271b1 !important;
			border-color: #2271b1 !important;
			color: #fff;
		}
		.mcg-currency-button-group .mcg-currency-btn:focus-visible {
			outline: 2px solid #2271b1;
			outline-offset: 2px;
		}
	';
	wp_register_style( 'idea-mcg-currency-buttons', false );
	wp_enqueue_style( 'idea-mcg-currency-buttons' );
	wp_add_inline_style( 'idea-mcg-currency-buttons', $css );
	wp_register_script( 'idea-mcg-currency-buttons', false, array( 'jquery' ), '1.0.0', true );
	wp_enqueue_script( 'idea-mcg-currency-buttons' );
	$js = <<<'JS'
(function ($) {
	function syncActiveButton($select) {
		var $group = $select.siblings('.mcg-currency-button-group');
		if (!$group.length) {
			return;
		}
		$group.find('.mcg-currency-btn').removeClass('is-active').filter(function () {
			return $(this).data('currency') === $select.val();
		}).addClass('is-active');
	}
	function initCurrencyButtonGroups(context) {
		$(context || document).find('.ginput_container_multicurrency select').each(function () {
			var $select = $(this);
			if ($select.closest('.gform_editor').length || $select.is(':disabled')) {
				return;
			}
			if ($select.siblings('.mcg-currency-button-group').length) {
				syncActiveButton($select);
				return;
			}
			var $group = $('<div class="mcg-currency-button-group" role="group"></div>');
			$select.find('option').each(function () {
				var code = $(this).val();
				var label = $(this).text().trim() || code;
				var $btn = $('<button type="button" class="mcg-currency-btn"></button>')
					.attr('data-currency', code)
					.text(label);
				if ($select.val() === code) {
					$btn.addClass('is-active');
				}
				$btn.on('click', function () {
					if ($select.val() !== code) {
						$select.val(code).trigger('change');
					}
				});
				$group.append($btn);
			});
			$select.addClass('mcg-currency-select-hidden').on('change.mcgButtonGroup', function () {
				syncActiveButton($select);
			});
			$select.before($group);
		});
	}
	$(document).ready(function () {
		initCurrencyButtonGroups();
	});
	$(document).on('gform_post_render gform_page_loaded', function (event, formId) {
		if (formId) {
			initCurrencyButtonGroups('#gform_wrapper_' + formId);
		} else {
			initCurrencyButtonGroups();
		}
	});
})(jQuery);
JS;
	wp_add_inline_script( 'idea-mcg-currency-buttons', $js );
}