JezK

Edit File: gallery-settings.js

/**
 * Jetpack Gallery Settings
 */
( function ( $ ) {
	var media = wp.media;

// Wrap the render() function to append controls.
	media.view.Settings.Gallery = media.view.Settings.Gallery.extend( {
		render: function () {
			var $el = this.$el;

media.view.Settings.prototype.render.apply( this, arguments );

// Append the type template and update the settings.
			$el.append( media.template( 'jetpack-gallery-settings' ) );
			media.gallery.defaults.type = 'default'; // lil hack that lets media know there's a type attribute.
			this.update.apply( this, [ 'type' ] );

// Hide the Columns setting for all types except Default
			$el
				.find( 'select[name=type]' )
				.on( 'change', function () {
					var columnSetting = $el.find( 'select[name=columns]' ).closest( 'label.setting' );

if ( 'default' === $( this ).val() || 'thumbnails' === $( this ).val() ) {
						columnSetting.show();
					} else {
						columnSetting.hide();
					}
				} )
				.change();

return this;
		},
	} );
} )( jQuery );