[MlMt] syntax in smart folders editor

[John Cooper]

Howard Wettstein wrote (at 22:53 on 21 Apr 2016):

> I’m trying to set up smart folders but find some of the syntax )(a 
> lot of it) hard to follow, I mean  in the drop-down lists. Is there 
> someplace I can find more or less detailed explanations?

This bothers me a lot, too. So much power, and so little information! 
I'm a pretty good reference sleuth, but I don't know how to even begin 
to decipher these, among many others:

Source > Path > Noinbox
Date > » Local > Formatted [why the chevrons? Formatted how?]
Subject > Blob
Any Address > » Identity [or » Correspondent] > User > Notag