I often find myself wanting to see all files and folders that match some pattern, such as car - is there a specific reason why this is not possible in Flat View (mixed)?
You have the option of filtering folders (as well as files) in flat view, but if a folder is filtered out of flat view then all of its contents are filtered out as well.
You also have the option of using Tools > Find Files to find whatever combination of things you want using as complex a filter as you want, which is the best way to do it if you want to find both files and folders matching some criteria.
I have been using Find Files, and also Query (Windows Search, resulting in "Search Results for ..."-"folders"), but I've been very heavily using Flat View in the last weeks, I'm basically using Flat View 90% of the time (not of 90% of all file searches, but 90% of OVERALL use time of DOpus!, and I find it to be absolutely superior and genius. If it were possible to filter for folders without hiding the contents of those folders not matching the mattern, Flat View would basically replace "Find Files" in 99% of situations. I prefer Flat View because it's "live" and updates immediately for any kind of changes (file change, new file, ...).
I usually name my files by category, such as "car - filename.pdf", similar to tags, which works great with Flat View. However sometimes I don't feel like mass-renaming 200 jpg files to "car - 7628.jpg", when they are already in a folder such as e.g. "car - pictures for selling old car". These 7434.jpg/... files will then not be found unless all folders in higher rank contain "..car.." in their names.
I'm so obsessed with FlatView I won't go back to Find -- instead, I will either put blank files into folders to make them retrievable (I will simply put 0 byte file "car - pictures for selling old car.folder" in to the folder).
Making sure that the "tag" car appears in all folders of higher rank won't work because sometimes I assign two tags, such as: "car, house - garage renovation", but of course that one can only EITHER be in the main folder "House" OR "Car", thus not showing up if I search for "car" if I put it in the main folder "house".
I'm just sharing this method also because perhaps other users might find it useful.