Trying to sort my mess out.
It seems I have a load of pdfs that have been tagged but not put in groups.
If I do a search for “tags>” I get a whole load of results, and if I hover over them no group name appears in the yellow box.
I am presuming that if I work my way through this list I will have found all documents not in a group? I cannot see how to set up a smart group to look for things not in a group.
As always, thanks!
Possibly all of your documents are in the so-called “top group” – it is the root group of your database, and is the parent of the database’s Inbox, Tags, etc. Click Go > Top Group, or the toolbar icon that looks like a house, or option-command-home key — all of these will take you to the top group.
BTW, it’s a good practice to occasionally visit the top group. It’s never obvious in a database that there are documents stuffed into the top group, and it’s often where “lost” documents go to hide 
omg; thank you, never crossed my mind to look in there; bet it end up looking like under the sofa cushions
I do seem to have tags, without groups and that also do not show up in the root folder you mention.
The problem seems to be if the tag is a sub tag of another it slips through the root level.
Not sure how to track them down. I am only finding them as I am converting web archive to pdf and the resulting pdf title is in blue.
Only way I can seem to find them is to go to tags and work my way through each one.
If its okay the location starts inbox>. if its not it starts tag>whatever.
Very glad I have found this out! Thought I had more documents in here as well.