Scenes

I thought I'd try creating a scene in HS rather than using an event.
When I go to the 'scene management page' and 'create a new scene' I get a drop down list of z-wave devices.
The drop down list only shows a small number of my z-wave devices - and crucially not the ones I want to use!
Should they all appear - and if so how do I make them appear?

Cheers.