Use the control_listings_svg_icons_{$group} filters to modify the array in your child theme. The filter is the best option. For example the to filter the social icons use the control_listings_svg_icons_marker filter in functions.php:

add_filter( 'control_listings_svg_icons_marker', 'my_theme_modify_marker_svg_icons' );
function my_theme_modify_marker_svg_icons( array $icons ) : array {
    // modify/add/replace $icons here
    $icons['travel'] = 'the new travel inline svg tags';
    return $icons;
}

The main icon groups are social and ui, ui will contain the menu and close options, much like social containsthe500pxandtwitter` options.