Add a script after initialising / starting the configurator

add-script-after-configurator-start.js

wp.hooks.addAction( 'PC.fe.start', 'Custom_script', function( configurator ) {
	// Do something here. E.g.: 
	// Get the viewer
	var viewer = configurator.viewer.$el;
	// Get the layer container
	var layers_container = configurator.viewer.$( '.mkl_pc_layers' );
} );

This script can be added using an external file, like this:

add_action( 'mkl_pc_scripts_product_page_before', 'custom_configurator_script' ) );
function custom_configurator_script() {
	wp_enqueue_script( 'my_custom_script', MY_URL . 'add-script-after-configurator-start.js', [ 'jquery', 'wp-hooks', 'wp-util', 'backbone', 'mkl_pc/js/views/configurator' ], filemtime( MY_PATH . 'add-script-after-configurator-start.js' ), true );
}

It can also be added inline using wp_add_inline_script, as done in some of the themes.