In DEVONthink To Go how can I find and list all documents in all groups of a database?
You can’t.
That’s a shame… 
I experimented with the NOT operator, but this keyword does not behave like a proper boolean negator. The query
xyz OR (NOT xyz)
(with and without the brackets) doesn’t seem to be understood although it looks to me like a proper boolean expression.
If this worked, we could create an all-document query! 