I can't work properly on one screen. Two and I'm fine. One and the day turns into a lot of moving between windows. I lose my place. I rebuild the same thought I already had twenty minutes ago.
For a long time I filed that under preference. Nice to have. The sort of thing you mention when someone asks what you need and you feel slightly awkward asking for it.
It isn't a preference. Most of what I do is holding one thing still while I work on another. The requirement open beside the design. The numbers open beside the document that explains them. On two screens that is one continuous piece of thinking. On one it becomes a sequence of small acts of memory, and I am not as good at those as I assume.
Which is why my Fridays have quietly reorganised themselves. Working from a café, on a laptop and nothing else, I stopped trying to do the work that needs two screens. I read. I answer things. I plan, badly, in a note I will never open again. The building work waits for a desk.
I thought I was choosing that. Lighter work on a Friday, sensible, everyone does it.
I wasn't choosing it at all. The desk was.