John
I use to have the same issue. What I did was create a field in the activitiesjobitmes table called Phases. I do landscape work so i want to group or as you would say choose where to create a new line item. I would then put that new field in the itmes grid. When entering line itmes, i put a number or letter or what ever group i want that item to be. I would then create a report with grouping in the details section.
I see this is your frist post so i hope i did not overwhelm you. I dont work for Method but im a end user. There are some great consultants here that would be able to help you with your issues.
John M