My recollection of the lumbar support button is that it involves some small "packets" of air, for want of better wording, inflating / deflating. On the old Club World seating there are some equally obscure buttons for this. If you operate them on quieter aircraft, you can hear something, and if wearing a t-shirt and no other layers you could detect some things moving around the upper back area. But yes, I'm not sure it was worth the effort, in umpteen flights it hasn't to my mind made a jot of difference to the travel experience.

There used to be a laminated card to explain all of this, I think it got Covidised, and I did have a hunt around since I vaguely recall someone putting up images from it, perhaps when the 789s came on stream. But alas, failed to find them. Jerry?