How to create a reusable subprocess

This seems like it should be easy. Drop a subprocess on the diagram, right-click, choose sub-process type, and choose reusable. That's what all the documentation I can find says.

But the only subprocess type that displays is Sub-Process.

Now if I go to the sub-process shape on the palette and click on the arrow, it shows 2 types: Sub-Process and Reusable Sub-Process. If I change it to Reusable Sub-Process and drop it onto a diagram, it changes into just a Sub-Process.

What am I missing?

Thanks,

Mike