- Edited
Feature request
When using the 3-finger-swipe to go back/forward, command could be a modifier key that causes the navigation to happen in a new tab.
Example use cases
This is useful when you've navigated to a new page but…
- …you want to compare what you saw on the previous page with what you're looking at now. (Eg. product comparisons)
- …you want to keep the current tab open for reference but continue browsing from the previous page (Eg. you've found an interesting search result that you want to hold on to for a while, but want to see what other search results have to offer)
- … you want to have another quick glance at the previous page, soon close the tab again and continue browsing. (Eg. "what did that previous article say about this article it linked to again?")
Extra motivation
This would be consistent behavior with command key modifying other navigation actions to to happen in a new tab:
- The return/enter navigation from the URL bar
- The click navigation from the back/forward buttons
PS:
This was also how Safari used to work before upgrading to the version included with macOS Yosemite. My feedback about this feature's disappearance in Feedback Assistant has gotten no response from Apple since 2014. 
Thank you for your efforts and consideration.
