Version: (using KDE Devel) Installed from: Compiled sources If the dolphin part is used inside Konqueror, the Show Hidden Files option does not appear (probably it is in the application, not the part).
*** Bug 155565 has been marked as a duplicate of this bug. ***
*** Bug 156435 has been marked as a duplicate of this bug. ***
I added this action (and many others) to the part some time ago (for 4.0.2 and 4.1), this bug is fixed.