The best way to see how much you are making is to use the project tags, but this would apply to the whole invoice not per line.
Not sure where the project features are going (in terms of future plans), but maybe @Glenn could comment further on that - I believe there are plans for project adjustments as per the post below, but I do know they’re always busy working away in the background.
http://community.quickfile.co.uk/t/projects-item-level-tagging/1858