Drag & Drop Upload - Save User Data

// Add hidden fields (for user_id )
add_filter('wpcf7_form_hidden_fields', function( $hidden ){
    $user_id = get_current_user_id();
    if( $user_id ) {
        return array_merge( $hidden, array('user_id' => $user_id ) );
    }
    return $hidden;
});

// Hooks after form sent
add_action('wpcf7_mail_sent', 'dnd_save_user_meta', 100, 1 );
function dnd_save_user_meta( $contact_form ) {
    $submission = WPCF7_Submission::get_instance();
    $posted_data = $submission->get_posted_data();
    $upload_field_name = 'upload-file-929'; //@note: change this to match  your upload field name
    if( $submission && isset( $posted_data['user_id'] ) ) {
        $user_id = $posted_data['user_id']; //coming from hidden_fields - filter
        if( isset( $posted_data[$upload_field_name] ) && $user_id ) {
            update_user_meta( $user_id, 'uploaded_files', $posted_data[$upload_field_name] ); // save to user's data
        }
    }
}