First off, everybody has to solve this sort of situation in their own way. All I can tell you is how things work for me, and you'll have to decide for yourself whether or not to incorporate it.

I have a similar system, though my context-sensitive Next Action lists are printed to index cards and my tracking software is SimpleGTD. When I complete a Next Action, unless it's absolutely obvious what the subsequent one might be, I don't bother with determining another until my next Daily or Weekly review. Hopefully your lists are complete enough that you'll have more things to do in that context without having to refresh the list all the time!

The other thing I do, though, is that I keep master "Action" lists for my projects in SimpleGTD. The service lets you write out any number of Actions for each project while only flagging those you can do right now as Next Actions. I don't keep those master lists with me at all times; however, since I have already thought out the project structure past the current Next Action, it's often easy to remember what else I have decided to do.

Finally, who says you can have only one "Next Action" per project? If there are multiple things in a project that are independently do-able (i.e. no waiting for yourself or others to do something else first), put them all in your notebook!