Enable VLAN backed segments on NSX deployment
If you build environment as per Configure NSX-T 3.0 from scratch with edge cluster and tier gateways then only overlay segments would be visible in vCenter for assigning to VM NICs. If you create any VLAN based segment (Connected gateway: none, VLAN-ID: X) then it wont be visible in vCenter. To solve this problem again configure NSX on each ESXi host and also add VLAN transport zone ( edge-vlan-tz ) along with overlay transport zone ( mg-overlay-tz ) on all ESXi hosts.
If you configure NSX on hosts using profile then editing the host profile might throw error. Edit the transport zones of nodes manually one by one to get VLAN based segment support.