You'll have to use a different icon/button. If you use the home icon/button, it only gives you two choices in the prefs.. "apps" and "favorites", I think.. so you can't really choose from a list of apps like you can with the other buttons. I chose to program the right-side button (looks like a globe) in the prefs, and I've quickly mastered the use of it.
I love ZL, by the way. I've used it since 2003, and have moved it over from my original Sony Clie T615, to a Tapwave Zod, to my current TX. The TX was the most difficult, simply because of the home icon/button issue.. so I had to think 'outside the box' a bit.
Hope this helps you work around the problem! Let me know.. perhaps I can assist further.