In filemaker portals may be used where you would use sub forms or sub reports in access.
There is a more flexible approach however. You can make your report a summary report based on your line items and group them under two sub-summary headers.
Here's a link to a simple tutorial on setting up summary reports that you may find useful:
Creating Filemaker Pro summary reports--Tutorial
I then want the quotation report to list all the included items and prices and then have a "Optional items" header and below that list the optional items. Only the included items will then be included in the total at the foot of the report.
You need a calculation field that will return the price only when the item is included, e.g. =
Case ( not Optional ; Qty * Price )