extend-display would be the most correct in my opinion, I feel like a lot of people would use
extend-desktop if they didn't think about it. But the tag usage frequency seems to prove me wrong.
When attempting to adjust the settings to extend your display, Windows does use the words 'Extend these displays`.
From all of my own personal experience, I noticed that almost everyone refers to their display as their desktop. "How do I extend my desktop?", "How do I mirror my desktop?", etc.
I went to the almighty Google to solve this and typed a query
Extend d and 4 results were:
- extend definition
- extend display mac
- extend display
- extend display windows 7
So I vote