If you save your preset, then you effectively are able to go back in, load up that preset, then make further modifications. As I mentioned above, there are just too many variables to account for to be able to read in a modified stylesheet after the fact. Saving/editing your presets still gives a lot of control. 
I understand. I guess myself and perhaps the two others who commented are just looking for some acknowledgment that our assumptions about the features of the product, although incorrect, were reasonable given our limited knowledge of CSS. It's the only extension that I've ever used that didn't allow editing via the visual interface.
Perhaps what I'm looking for at this point is a visual stylesheet editor - I haven't really looked for any so I don't know if they exist - perhaps not due to the reasons that you mentioned.
But don't forget that we are developers too! We've all been in the situation of attempting to explain compexities of applications we're asked to create to those who ask for certain features assuming they're easy. And in many cases, there is a solution to those complexities to give what's been asked for.
So, from your explanation, it sounds like the major factor is the difficulty in opening a style sheet for editing in the visual interface that's been edited elsewhere. But what about if it hasn't been touched - would that be something to consider? I think it may be a starting point..
Now, regarding editing the presets. What would be the process if I've created my initial layout and saved a preset, then created several pages from that, chock full of content. Do I open the preset, edit it and then create a new page from that - mostly as a template sorta - just to re-generate the style sheet that the others are referencing?
Thank you for your input on this topic - despite these issues, I think it's still a very fine and useful extension!
