When you add a compute manager, NSX Manager adds its identity as an extension in vCenter Server. If you remove the compute manager, the extension in vCenter Server will be removed automatically. If the extension is not removed for some reason, you can maually remove the extension with the following procedure.
Enable access to the vCenter Server Managed Object Browser (MOB) by following the procedure in https://kb.vmware.com/s/article/2042554.
- Login to the MOB at https://<vCenter Server hostname or IP address>/mob.
- Click the content link, which is the value for the content property in the Properties table.
- Click the ExtensionManager link, which is the value for extensionManager property in the Properties table.
- Click the UnregisterExtension link in the Methods table.
- Enter com.vmware.nsx.management.nsxt in the value text field.
- Click the Invoke Method link on the right hand side of the page below the Parameters table.
The method result says void but the extension will be removed.
- To make sure the extension is removed, click the FindExtension method on the previous page and invoke it by entering the same value for the extension.
The result should be void.