custom post type by author – wp job manager

As others have stated, you are going to want to add an argument to your shortcode to set a specific author_id. Once you have that you can then perform your query.

I have not tested, but the following code should put you on the track. The shortcode would be [query_my_posts author_id=”#”]

function custom_shortcode() {
    $atts = shortcode_atts(array(
        'author_id' => '',
    ), $atts);

    $args = array( 
        'post_type' => 'job_application',
        'author'=> $atts['author_id'],  
    );

    $loop = new WP_Query( $args );
    while ( $loop->have_posts() ) : $loop->the_post();
        the_title();
        echo '<div class="entry-content">';
        the_content();
        echo '</div>';
    endwhile;
}
add_shortcode( 'query_my_posts', 'custom_shortcode' );