I need to group different kind of items and services into the same estimate to help me and my clients understand better my proposal and allow me to have more control over the overall estimate. 

For example, first group would be: PREPRODUCTION, where I'll stack items such as Location Scouting, Casting, Some travel and set design. The second group will be PRODUCTION, which will be populated with  cameras, lights, technicians, etc... And the third group will be POST PRODUCTION, with items like editing, animation, music, voice over etc. It is very important for me to see the sub total on this categories in the same estimate.