When you set rate-limit in PPP profile or DHCP or Hotspot the router creates a dynamic queue in Simple Queues.
How do to get the router to create queue in Queue Tree instead of Simple Queue?
You can’t. Queue tree isn’t meant to put each target ip separately as a child in a queue tree. You could rather put a queue tree child for an ip range with a limited pcq-rate and put clients on separate ranges manually or by radius authentication.