How do I use wp_editor() in widget form?

I stumbled across this solution a while back; this might be what you are looking for:

I added this to my theme’s functions.php file…

// First, I created a shortcode for a function, that would typically be inserted in to a template file, so that it could be inserted in to a widget.

add_shortcode('myshortcode', 'myfunction');
function myfunction() {
  if ( function_exists( 'get_smooth_slider_category' ) ) { get_smooth_slider_category('featured'); }
}

// Then you can add this to allow shortcodes to be used in widgets.

/* Make shortcodes work in widgets */
add_filter('widget_text', 'do_shortcode');

Then I just added [myshortcode] to the text widget and viola; I have a function in a widget.