Just switching over from Evernote—a program that has become an absolute disaster.
I am very happy with Devonthink so far.
I have a simple question that likely has a straightforward fix:
My filing system consists of a series of top-level folders with subfolders in each. When I click the top-level folder no items show up the list. I would like to be able to view the contents of all the sub-folders within the top-level folder. Is this possible? Thank you.
Not unless you switch to another view, like Split view, and open the folders. Three Pane view will not show the contents of all a groups subgroups.
You can create a Smart Group with the Search in: pointed to a group and criteria of Kind is Any Document.
Thank you kindly for your reply. The smart group idea was a perfect workaround. Thanks!
You’re welcome. 
If you are using 3-pane view you can select the top level group and the subgroups underneath it – in the groups pane. In the documents list pane you will then see a list of all the documents inside those selected groups. Finally, if you turn on View > Cover Flow then you’ll be able to browse through previews of the documents.
You don’t need to select all subgroups – all you need to do is use command-click to chose various groups from the groups panel and you’ll get the list of their documents in the the documents list pane.
The View menu is fun to play with all its options when you have a few spare moments and want to experiment.