Regarding lying down to work + body structures that "lack blood supply and are nourished by diffusion", a cautionary anecdote:
[TLDR: Typing for long periods while lying down with hands elevated above heart may cause an injury.]
A few years ago I built a lying down / "zero gravity" workstation. The position of my keyboard was very similar to the Altwork station, I.E. with arms bent at about 90 degrees with a keyboard and trackpad positioned above my body.
After a couple months of using it during full time working hours I developed severe pain in my wrists and forearms. This had never occurred before when using a conventional workstation / position. I soon became unable to type, and nearly any use of my hands resulted in intense pain. Writing code using a keyboard was out of the question.
After much reading during my forced hiatus, I came to a hypothesis: elevating my hands to type while on my back caused a decrease in diffusion of fluids to the non-vascular tissues of my forearms and hands, that is, the tendons and muscle fascia. While in this unlubricated, "dry" state, the small, continual movements of the tissues against each other (the motions of typing) led to the injury. I concluded it was tendonosis. (IANAD, but had no health insurance at the time.)
The injury took six months to fully heal, during which time I self-administered massage, myofascial release therapy, and grip strength training to increase circulation around the various tissues. For much of that time, I could barely work. Truly it was hell.
As for the workstation, I modified it to use a split keyboard (Ergodox EZ) that kept my hands below my heart (basically at my sides). But ultimately I abandoned the whole thing after failing to achieve a reasonable touch typing speed with the Ergodox.
My current workstation is based on an Ikea lounge chair and ottoman. Keyboard and trackpad extend from the side into my lap on a low-mounted, adjustable arm. The monitor is also on an arm, cantilevered out over the ottoman (and my legs) at a comfortable viewing angle and distance. This setup is certainly not as relaxing for the back as the previous zero gravity position, but in approximately three years of use I've had no further injuries from typing.
YMMV.