For me, "study" is the kind of next action that will make me go numb to my lists. I tend to order my coursework this way:
30,000 ft (1-2 year): Have a successful school year with x grades and y papers submitted to conferences
20,000 ft (Areas of focus): Class A, Class B, Class C
10,000 ft (projects): Class A midterm paper, Class B final paper
NAs: @Any Computer -- get on Google Scholar and find 25 sources to read abstracts (for Class A midterm paper)
@Desktop Computer -- print out forms for Institutional Review Board application (for Class B final paper)
"Reading" for classes I more or less treat as a context unto itself--at my weekly reviews, I load my weeks' readings onto my tablet PC and my Sony reader, and then i have a GDocs spreadsheet where I list all the readings I need to do in the order they're due. Then I make it a point to get myself to an @reading context a couple hours a day and crank out whatever I can until either a) I've run out of steam or b) I've run out of time or c) I've prepared adequately for the next two days' worth of classes.
The other thing that it sounds like your work lends itself to is some kind of checklist. I think "study" is probably still at least at the project level for you, because it involves NAs highlighting, taking notes, etc. But you could create a checklist for yourself for each unit you want to study, add a unit to your projects list and some sort of NA that will serve as a stake for you to go back to that checklist, and use the checklist.
Don't overlook the power of checking things off as done! "highlight" as an NA will make you feel very good when it's finished. It might seem menial and repetitive, but if it helps you stay engaged with your list and feeling completion, these are good things.