[lnwlebjel]

This is the best one:

  # Display full POSIX path as Finder window title
  defaults write com.apple.finder _FXShowPosixPathInTitle -bool true

I don't know how anyone knows where their stuff is without it.

[bartvk]

Wow, that's extremely useful!

There is an alternative, in the Finder view menu -> Show Path Bar. It's displayed at the bottom. This will display the path of the current selection, or -- if nothing is selected -- the currently opened folder.

[ataylor32]

Hold the command key while clicking the title of the Finder window

[librarianscott]

Do you mean the collapsed titlebar/toolbar that is the default in Big Sur?

[ataylor32]

Yes, and it works in previous versions of macOS as well