Yep. That's all fine so far.
The VM (which runs perfectly fine in ESXi and I use the console)... started out life as a VMware Workstation guest.
I used VMware Workstation and "uploaded" it right to the ESXi .. and.. bingo. It's in the inventory. Yay.
Now I cannot right-click on it and make it a template. There's just no option to do so.