Is there a way to lock research paths?

[Aleph]

Generally I find that more often than not (now there's a confident statement) that the last bar modified becomes the one primarily affected by subsequent changes. For example, I have alteration up. I then add conjuration. I then add thaumaturgy. If I then go and tinker with conjuration or alteration, thaumaturgy will be primarily affected since that was the one I just did.

Like I said, though, just an impression.