I've been a software engineer for over 15 years and so have been working at a desk for just as long. For the first few years I never thought twice about it, just sat all day long, no big deal. Eventually that started to catch up with me and my health began to noticeably decline.
I eventually made a conscious effort to combat the sedentary nature of knowledge work and have since seen significant improvements in my health, both physically and mentally. I now have this dichotomous relationship with computers: on one hand I love programming but on the other I can't stand being sedentary and I don't like that the default mode for computer work is sitting at a desk completely stationary.
So I'm always looking for the most effective way to maintain my well-being while also working at a desk all day and I've been writing about it on my blog. It's rough at the moment but am actively working to improve the content and quality; but I think this article in particular may be of interest: https://healthyhacker.co/how-to-improve-your-health-with-an-....
I think there are the obvious answers like: go for walks, go to the gym, do active things, etc. I'm 100% for all of those, but for the most part you can't really do any of them while working. But movement is the key and so I think the most important thing you can do at your workspace is to create a movement-rich environment where you are constantly able to shift positions and fidget. Ideally get a standing desk; this sets the foundation... you'll have a difficult time being sedentary while you're standing. This keeps the lower half of your body active; i.e. muscles are engaged and circulation is flowing. And then from there you can add additional activities such as putting a ball under your desk that you can prop your foot on and move around.
It's also vital to actually step away from your desk once in awhile as well. One of the most effective things you can do relatively easily is go for more walks. No equipment necessary; just get up and move (with a standing desk you're already half way there). It also has the added benefits of clearing your head, which as we know mental clarity is vital to knowledge work.
To answer your specific question, what's the cutting edge of doing knowledge work while not being stationary... it might not be a fancy answer, but I think it's simply just moving more.
Also, I highly recommend the book Deskbound by Kelly Starrett (https://www.amazon.com/gp/aw/d/B01E1HDJ64). It is my main resource so far for all this information and I have found it incredibly helpful in learning how to become a healthy hacker. And here's the presentation he gave that inspired the book: https://youtu.be/kfg_e6YG37U.