When adding additional line items to a form, I assume you are referring to a table within a from (e.g., InfoPath allows a table within a form: http://office.microsoft.com/en-us/infopath-help/insert-a-repeating-table-HP010080916.aspx)
The qListForm does not have embedded tables within it so you can't add additional line items to a qListForm. A work around or an alternative technique is to use a parent/child approach with two different web parts. For example, say you have a customer displayed in qListForm and you want to add contacts (rows). You could setup a customer using qListForm on a page and under it put a qListView on the same page to show the contacts. The contacts table would have a column (e.g., CustomerListID) which links it back to the customer (parent). When you click "New" Contact, the CustomerListID could be configured to be filled in automatically through a session variable. This approach shows two parts on the page: 1) qListForm on top and 2) underneath qListView which is filtered based on a web part connection on CustomerListID.
If you want to show the two web parts as a single web part, one approach customers take is to use the freeware "EasyTabs" which you can review and download here: http://sp2010.pathtosharepoint.com/sharepoint-user-toolkit/Pages/Easy-Tabs-v5.aspx. Easytabs, puts all of the web parts on a page into a single, tabbed web part.
I hope this helps solve the rows in a form use case.
PM, Quest Web Parts for SharePoint