Those are hard coded into Poser. Easiest way is to copy the channels from an existing figure. If you have not already got it get this free CR2 editor by John Stallings from:

http://tech.groups.yahoo.com/group/PoserTECH/files/

Open your figure's CR2 file in the left hand pane.
Open the P4 male CR2 in the right hand pane.

Scroll to the hand actor.
Expand to see the channels.
Copy the Grasp, Spread and thumb grasp channels over to your new figure.

Later Poser figures use ERC code which is different so don't be confused by that.