Show only those pages that are created by the specific logged in user in WordPress

Add the following to an mu-plugin (custom user role is so76666381) (tested):

// Adjust admin queries to only show pages by current user if has custom role.
add_action( 'pre_get_posts', static function ( $query ) {

    // Limit hiding pages only to admin queries.
    if ( ! is_admin() ) {
        return;
    }

    // Get post types from query.
    $post_types = ( array ) $query->get( 'post_type', array() );

    // If pages are not being queried, bail.
    if ( ! in_array( 'page', $post_types ) ) {
        return;
    }

    // Get user's current role(s).
    $roles = wp_get_current_user()->roles;

    // If user does not have custom role, bail.
    if ( ! is_array( $roles ) || ! in_array( 'so76666381', $roles ) ) {
        return;
    }

    // Limit results to those by current user with custom role.
    $query->set( 'author', get_current_user_id() );
} );