This is the question what [Unfiles] smartfolder is for.
This folder seems to show files that remain in [Files] folder and NOT in sub-folders beneath it. It may be useful for pre-filtering to reduce number of files in the Search action.
In my case, however, almost files (1049/1458) remain in [Files] folder and sub-folders are used only for specifying series of web pages to some theme (409/1458).
If user has custom to move captured files to sub-folders and [Unfiled] folder has small number of files, this folder may show Recent captured files.
However, I use [Recently Added] folder to find just captured files and sometimes use [date] option of Record Lists.
So, I have confused about what [Unfiles] folder is planned for originally.
I appreciate to get any advice about this.