Back in March, Dan Moren wrote an excellent post on macOS Safari, and switching tab behavior, so new tabs open at the end, instead of immediately after the current tab.

This involves enabling the Debug menu (not to be confused with the Develop menu, which is exposed in Safari Settings > Advanced).

In a nutshell, to enable the Debug menu, hop into Terminal and type:

defaults write com.apple.Safari IncludeInternalDebugMenu YES

Relaunch Safari, and take a look at the last two submenus in the newly appearing Debug menu: Tab Ordering and Tab Features. Good to know.

Interested in some under the hood details of the Defaults mechanism, and moving Prefs files? Check out this writeup from Jeff Johnson.