How can I create a Saved Search that excludes a specific folder from the results?
If you hold option the (+) button to add a search criteria will become a (…) and an Any/All/None block. Set this to None.

For the criteria select Document Container. It won't be in the default list alongside Name, Kind, etc. Select Other… to select it from a list of additional criteria so long it has its own search feature:


Set this to the name of the folder that you'd like to exclude using whatever is/contains/begins with/ends with you find suitable.

The end result should look something like this: