I suggest rethinking file browsing function especially for "Files" section (but for "Favorite places" too - see Bug310203). Instead of browsing I would prefer to be able to add there some favorite or just temporary files I currently work with, like some pdf's or odt's documents for quick access, if i have them in different folders on my hard disk. Perhaps this could work like some shortcuts to files. What would be important here is to be able to add them easily. For me personally that would be far more useful than coping Dolphin's browsing function. I'm not sure if this is possible but if it is that would be awesome. At the moment to access such "current" files I have to throw them to one folder for example a Desktop folder. But this is not my preferred solution. Recent documents neither give this solution because they very quickly change its content.
This should be doable by creating a "Favorite Files" source, and modifying the "Dir" source to allow favoriting files in addition to folders (folders already go to "Favorite Places", files would go to "Favorite Files")
Hello! Sorry to be the bearer of bad news, but this project has been unmaintained for many years and I will be closing this bug.