The Events Calendar: Display WordPress custom fields in the Item Details part of the List Venues Organizers Shortcode extension.

functions.php

<?php
/**
 * The Events Calendar: Display WordPress custom fields in the Item Details part of the
 * List Venues Organizers Shortcode extension.
 *
 * Excludes hidden fields (beginning with `_`) and Elegant Theme's hidden fields (beginning with `et_`).
 * Authored by Richard of memberwise.org.uk and Clifford (Tribe Support).
 *
 * @link https://gist.github.com/cliffordp/a6cff51ed56276641c4d4ea0a82b25b9 This snippet.
 * @link https://theeventscalendar.com/extensions/list-venues-and-organizers-shortcodes/ Extends this extension.
 *
 * @param string $item_details
 * @param int    $post_id
 *
 * @return string
 */
function tribe_ext_list_venues_organizers_show_wp_custom_fields( $item_details, $post_id ) {
	foreach ( get_post_meta( $post_id ) as $field => $value ) {
		$field = trim( $field );

		if ( is_array( $value ) ) {
			$value = implode( ', ', $value );
		}

		// Exclude hidden fields
		if (
			0 === strpos( $field, '_' )
			|| 0 === strpos( $field, 'et_' )
		) {
			continue;
		}

		$value = esc_html( $value );

		if ( '' === $value ) {
			continue;
		}

		$item_details .= sprintf( '<strong class="%s">%s</strong>%s<br/>', esc_attr( $field ), $value, PHP_EOL );
	}

	return $item_details;
}

add_filter( 'tribe_ext_list_venues_organizers_shortcodes_item_details', 'tribe_ext_list_venues_organizers_show_wp_custom_fields', 10, 2 );