I did manage to accomplish this with a native wordpress function.
add_action( 'save_post', 'change_meta_on_update', 100, 3 );
function change_meta_on_update( $post_id, $post, $update ) {
$new = get_post_meta( $post_id, 'titel', true );
update_post_meta( $post_id, 'profile_subtitle', $new );
}
Simply this fires after the post update (prio 100). Takes the value I wanted from ACF (“title”) and then updates the other value (“profile_subtitle”).
🙂
