Works out of the box, easy to customize

If you want this to apply to custom post types, simply modify the following line in the plugin:

function mypo_parse_query_useronly( $wp_query ) {
    if ( strpos( $_SERVER[ 'REQUEST_URI' ], '/wp-admin/edit.php' ) !== false ) {

To include the endpoint of the edit page for the custom post type, like so:

function mypo_parse_query_useronly( $wp_query ) {
    if (
    strpos( $_SERVER[ 'REQUEST_URI' ], '/wp-admin/edit.php' ) !== false
    ||
    strpos( $_SERVER[ 'REQUEST_URI' ], '/wp-admin/edit.php?post_type=[POST TYPE SLUG]' ) !== false
) {

You can add as many custom post types separated by OR operators “||” as you’d like.