Let's say I'm on a specific page within a web app. Maybe I'm typing out a comment on that page. Before I can hit submit, I need to reference something elsewhere in the app, perhaps on the previous page.
I can cmd+t to open a new tab, type out the URL, hit enter, and then navigate
around until I find the page I'm looking for. I do this exact thing sometimes,
but it feels slow and clunky.
The other way I accomplish this which feels way smoother is to duplicate the
current tab. I can do that by cmd-clicking the reload button next to the URL
bar.
This opens another tab at the same URL with the same navigation history. I can switch to that tab and hit the back button to go to the previous page, find the thing I wanted to reference, and then return to the previous tab to finish what I was doing.
To give a more concrete example: this happens all the time with GitHub PR comments where I want to copy the URL or number of a specific PR to reference in a comment I'm leaving on the current PR. Duplicating the tab, going back to the PR index view, finding the other PR, and copying its URL -- to me that is a quicker flow popping open a fresh browser tab.