Example to use the User List Dropdown for Customizer, the classes are inside the project: https://github.com/bueltge/Wordpress-Theme-Customizer-Custom-Controls

example.php

<?php
/**
 * @see: https://github.com/bueltge/Wordpress-Theme-Customizer-Custom-Controls
 */
add_action( 'customize_register', 'fb_customize_register' );
function fb_customize_register( $wp_customize ) {
 
	require_once( 'class-user_select_custom_control.php' );
	
	$wp_customize->add_section(
		'my_theme_blog_featured_user_list', array(
			'title'         => __( 'Featured User List', 'textdomain' ),
			'priority'      => 36,
			'description'   => __( 'Manage User List', 'textdomain' ),
		)
	);
	
	$wp_customize->add_setting(
		'featured_user_list_1', array(
			'default'       => __( 'Default User', 'textdomain' ),
		)
	);
	
	$wp_customize->add_control(
		new User_Select_Custom_Control(
			$wp_customize, 'featured_user_list_1', array(
				'label'       => __( 'Featured User List 1', 'textdomain' ),
				'section'     => 'my_theme_blog_featured_user_list',
				'settings'    => 'featured_user_list_1',
				'description' => __( 'Select a User from List', 'textdomain' ),
				'query'       => array( 'role' => 'author' ),
			)
		)
	);
	
	return $wp_customize;
}

Greetings,

I currently use your excellent "Multisite Enhancements" plug-in, and found this project when looking to see what other helpful things you may have created. I've done a ton of web development over the years (pretty much HTML, CSS, and JavaScript/jQuery), but am just learning PHP and the wonderfully complex underside of WordPress.

I'm pretty familiar w/ adding PHP code sections to my WP installation (via functions.php, shortcodes, and per-page injection). I have recently added a function to populate a Gravity Forms dropdown w/ a list of WP registered usernames, but I would much rather use an established code-base from a seasoned developer. :)

Anyway... I hoping you would be willing to explain a bit more about how someone like myself could begin implementing your "Wordpress-Theme-Customizer-Custom-Controls".

Cheers, Dustin