In social organisms this is called https://en.wikipedia.org/wiki/Stigmergy and means the way that instructions can be 'written' onto the environment (i.e. ant pheromones).
In theory no set of instructions makes sense outside a compatible environment. All instructions are implicitly bound to a reality where they make sense.
The idea of neural processing and signalling happening outside what we generally think of as the nervous system has me wondering about how oders are processed by insects.
E.O. Wilson has written of a "chemical grammar" of ants, and the relative characteristics of, say, danger or alarm signals, versus food or "friend" signals.
An alarm signal should propogate quickly, be easily recognised, and dissipate relatively quickly (no need in being alarmed long after the danger has passed). There's little concern that it be identifiable to other species. Small, light, volatile chemicals serve this.
A food or "friend" identifier should be persistent, fairly durable, and not be the same between different species (for various reasons). Larger, heavier, and less-volatile chemicals serve this.
The thought's occurred to me that with simple neurological systems, insects may have adapted neurochemicals to serve as exosomatic message transmitters (or maybe I'm getting this backwards and neurotransmitters have evolved from simpler chemical signalling). Which would make the "hive mind" a reality in mire than just metaphor.
Extending the concept, trees and plants with their massive surface areas make for a potentially very capable chemical emission and detection system. It was only after thinking that the branches (and roots) of a tree resemble the dendritic structures of neurons that I caught myself remembering that "dentrite" means "tree". So, yeah, doh!
It also suggests that whilst individual trees don't think, forests might....
I love the concept of "Human Cognition as Spider Web" analogy, because it certainly explains why I have, err, drastically faster synaptic response, recall, free association, and occasional synesthesia than most people I meet. Essentially a fiber optic network that needs a Controller of sorts (conscious mind) and a Library (long term memory) and bam, anywhere you want to go and anything available is nearly instantaneously available. That's when the "Dead Ends" and creative association kick in, funneling the energies downstream.
A lot of what gives this perception validity, to me, is the scientific research and discoveries regarding the elasticity and compensation dynamics of an injured brain. Sure, there are some basic paint-by-numbers functions (ex: sympathetic nervous?), but regarding the grey-matter and our notion of consciousness, it's a much more distributed, almost holographic model...or, just a really kick-ass web of energy and information...
In turn, this is why I hope when my mortal battery finally drains or gets shut off, my energy thingy rolling around in my human noggin can return to the Universal source from which it shoved it into this meatbag.
Isn't this what we call "muscle memory"? To regard this as an "extended brain" looks a bit like sensationalism to me. My keyboard and my shortcut-utility aren't part of my extended brain, but highly productivity-enhancing tools, as is the web to the spider.
It depends on where you personally draw the line between self and other. It's arbitrary really. Your example of a keyboard as an extended mind may be perfectly valid if you extend your sense of self outwards if only just a bit.
In theory no set of instructions makes sense outside a compatible environment. All instructions are implicitly bound to a reality where they make sense.