Sure. I think we could add a lot more detail (and subtract a few mistaken neurological notions from his system), but his basic idea still makes sense today:
The world outside the nervous system.
The nervous stimulation event. EG, light hitting the retina. This includes “immediate physical-chemical-electro-coloidal” impact of the stimulation, but I’m not sure where he’d draw the boundary.
Broader but still preverbal reactions. Thinking, feeling, etc. This is (at least in part) what Focusing is trying to access.
Linguistic, symbolic processing. “I see a chair”, “I feel hurt”, etc.
He refers to 1-3 together as “the silent level” and places emphasis on trying to properly distinguish, and access, the silent level.
I’m not sure whether 4 included the internal monologue, or only actual speech. If not, it seems like Korzybski must not have thought in words. (Note how “thinking” is placed as part of the silent level, in #3.)
The internal narrator is only one form of thought.
One meditation technique is to quickly label each passing thought (it’s called “noting” I believe). At some point you can begin to label the narrator process itself and see it separate from your other thinking processes (“voice” I call it, though it becomes wordless at that point).
[Edit: nevermind the Focusing link actually mentions the labeling. Though I recall Focusing was more about depth of analysis, not fast, high frequency labeling]