For one of our customers all NSX related questions are routed to me (pun intended). I received a customer ticket stating that they where not able to remove an unused NSX created port group although it is not in use while observing from vCenter.
After some investigating within NSX it was clear that this issues was caused by an orphaned logical port. NSX allows you to do allot of the config from the UI, but for some actions it is required to turn to the application programming interface (API). NSX provides a programmatic API to automate management activities. The API follows a resource-oriented architecture by using JSON object encoding. Clients interact with the management plane by using RESTful web service calls over HTTPS.