In general you cannot disable a module. Whether or not a module appears or lights up is controlled by the purchased license key. However, for certain modules (i.e. SQL Tuning and PL/SQL Knowledge Xpert) that require you to install it, you can prevent access by un-installing it.
If you really want to disable a module please contact Quest sales for specific trial keys that only includes the modules you want. Quest sales can be reached at 949.754.8000.