Add a custom control to an existing Elementor widget

code.php

// This example will add a custom "select" drop down to the "Image Box" 
// This will change the class="" on the rendered image box so we can style the Image Box differently
// based on the selected option from the editor.
// The class will be "my-image-box-style-blue" or "my-image-box-style-green" based on the selected option.

add_action('elementor/element/before_section_end', function( $section, $section_id, $args ) {
	if( $section->get_name() == 'image-box' && $section_id == 'section_image' ){
		// we are at the end of the "section_image" area of the "image-box"
		$section->add_control(
			'my_custom_control' ,
			[
				'label'        => 'My Label Here',
				'type'         => Elementor\Controls_Manager::SELECT,
				'default'      => 'blue',
				'options'      => array( 'blue' => 'Blue Style', 'green' => 'Green Style' ),
				'prefix_class' => 'my-image-box-style-',
				'label_block'  => true,
			]
		);
	}
}, 10, 3 );

Requires to add namespace and use at the top of the file, then is perfect.
The right solution to convert global arrays of fields common across different widgets, as we were doing with WPBakery page Builder.
Thanks for this goo dhint ;)

Just like you are using Prefix_class to add the selection to classes ... how can we add an attribute based on the selection?

hey @shikharpatel5 that's exactly what i'm looking for, did you find a solution ?