In Rule Machine, we can create an incomplete "?" or "NULL" Trigger Event using "Periodic schedule" with these settings: "Select periodic frequency *" set to "Daily", "> Every n days?" left unset, "> Every weekday?" left unset, "> At time" set to anything.
Rather than create a junk trigger, the software could default to "Every 1 days"
(which is what I expected when I chose "Daily").
If no default is desired, the software could insist that one of "> Every n days?" or "> Every weekday?" is set, otherwise a junk "?" trigger is created.
