Mutiple sites on custom ports on the same domain

Hi!
There is a common need to publish the same domain on multiple custom port and forward them to multiple backends at the same time.
Currently I can onyl add listen custom_port; directive in the advanced config but there is no way to define other backends.

If I add a new proxy host with the same domain and another custom port it still says the domain is already used.
if I add custom server{} configs with dirrent listen ports and proxy_pass backends - nothing works at all.

Please add the support for mu;tiple cutom posts for a single domain.

Thanks!

Start by reproducing the same-domain setup with multiple custom ports, comparing the existing advanced listen custom_port; behavior with proxy hosts and custom server{} configurations using separate proxy_pass backends. Define the expected port-to-backend behavior and identify the validation and generated Nginx configuration involved; done means each custom port routes the same domain to its intended backend.