After publishing a web app or other module to a server, the show in -> File Browser action is missing if:
1) You are on linux, and
2) /usr/bin/nautilus does not exist, and
3) /usr/bin/konqueror does not exist
After some research, it seems the best most universal way of opening a file explorer is via /usr/bin/xdg-open which seems to be available in more environments.