Hi Giovanni,
We have changed the way things worked because we wanted to remove a lot of the hocus-pocus that happened previously. Adding classes and resources to process deployment archives should be considered carefully and used only in a limited way. It should be realized that each of those classes and resources will be added to the process database for each version of the process. With the previous approach clicking a checkbox could result in inadvertently adding megabytes of classfiles to the archive. This is not desirable.
Now if you still want to add a lot of classes and resources to your process archives, the advised way to do this is using ant scripts. Constructing the process archives then becomes as easy as running the script.
Hope this helps,
Koen