You can only set initial values on the newer products and network products (the units that have Integer & String Variables).

My work around for the MX-980 was the create a "Welcome" page that basically said "Welcome to your Remote Control" - it would have a continue button that would set all my "initial variable values" and the jump to a new page. Then I would edit the "Watch" page (or whatever I set it to) to jump to the proper pages instead of the startup page.