How to enqueue js script after another specific js script?

That’s part of the default functionality available in wp_enqueue_script/wp_register_script.
The third argument, as seen in the official documentation of enqueue/register script, https://developer.wordpress.org/reference/functions/wp_enqueue_script/, https://developer.wordpress.org/reference/functions/wp_register_script/, is the dependencies array.

$deps string[] Optional
An array of registered script handles this script depends on.
Default: array()

So lets say you have script with the handle “sliderjs”, using your code it would look like this

function wpb_adding_scripts() {
    wp_register_script('egovt-add-js', get_stylesheet_directory_uri() . '/add.js', ['sliderjs'],'1.1', true);
    wp_enqueue_script('egovt-add-js');
}
add_action( 'wp_enqueue_scripts', 'wpb_adding_scripts' );

// A multi line arguments example
/*
wp_register_script(
    'egovt-add-js',
    get_stylesheet_directory_uri() . '/add.js',
    ['sliderjs'], // <- this is the dependencies arrray
    '1.1',
    true
);
*/