Been developing software for 30+ years, with up to 2 extra monitors, and I always go back to a single display. I'll put myself up against anybody with multiple displays. The thing is, I just alt-tab (or otherwise) to different things - it's not like I can actually perceive more than 1 window at a time, for the most part. The head twisting to see multiple displays bugs me, as does the eye movements across a huge display. Plus there is just more opportunities for distractions with more display area.
Finally, I work most effectively when I hold what I need in my head, and find that multiple displays fights against that need.
The only real exception to that is if I'm writing front end code of some sort, having the live updates helps a ton.
Lastly, if I could have a bigger display on my laptop, I'd be up for that!
I used to feel this way. I found it depends on the work.
A lot of my old work didnt depend heavily on looking at a terminal output constantly.
These days, i have to have about 3-4 things running. The extra screen just becomes a log window.
You can argue the software should be redesigned, i do too, but the problem for me remains and a second screen while not solving it, alleviates it a lot.
It might have something to do with using a twm, might not.
All i know is that i dont miss the days of tab cycling and desktop flipping.
Tab cycling can be a productivity killer, especially when you need to cycle between more than 4–5 applications (which can happen quite often, but OP wrote “alt-tab (or otherwise)”.
What works excellent (at least for me, not necessary for you) is to set shortcuts to your most used applications (be it the function key row, or some hjkl combinations). With such a setup you can just press a key / combination from muscle memory, instead of opening the tab switcher overlay, parsing it, deciding how often you need to press tab, and then actually switching to the other application window. Keeping shortcuts to applications feels like you would only have to do the last step.
With a laptop, an extra screen does seem to help somewhat in situations like you describe, I agree. That's because a laptop screen isn't quite big enough to bother with tiling your windows. If I had a laptop with a 20" display, maybe a touch bigger, it would be plenty for 95% of my development needs.
But since those don't exist, my general preference is an available external screen that I can use if needed. I like to couch/chair code a lot with my legs up, so I don't like to rely on an external monitor, so I try not to get used to one full time.
Finally, I work most effectively when I hold what I need in my head, and find that multiple displays fights against that need.
The only real exception to that is if I'm writing front end code of some sort, having the live updates helps a ton.
Lastly, if I could have a bigger display on my laptop, I'd be up for that!