I have noticed in one of my K2 smartform client events that I have differing behavior in the 2 configuration steps: transfer process data to form and transfer form data to process. 

I have seen this on multiple forms so I think it is either a bug or by design, but basically on the "Transfer Process Data to Form" screen I have the ability to transfer K2 process-based variables to the K2 SmartForm. All controls on the form are available as recipients of the data.

However, if I proceed a few screens and make it to the "Transfer Form Data to Process" screen, most of the controls disappear as if they are ineligible for copying data from the form to the process. I am not sure if this is a product issue or if I'm just not doing something correctly. What am I missing here?

I have noticed that it seems like controls where K2 KNOWS there will be data are available for transfer.  For instance, all radio controls show up, as do controls that contain smartobject lookups.  It is like the client event will only let you specify a control to copy data from form --> process if it knows for certain based on configuration that data should be there.