"Smart Folder" in macOS allows users to view a list of files or folders that share common characteristics. While leaving all the files and folders that match certain criteria at their original location, users can view all of them at a glance in a single place.
This kind of feature is especially suitable for Dropbox for the reason that we store thousands of files on Dropbox and do not leave a copy at our local computer, and we rely on the Dropbox web version to find the file we want. But searching with multiple criteria is never easy on Dropbox.com, and not to mention users need to find a way to save the search result each time.
For example, a user stores his travel photos by year, under each year folder are month folders, and in the month folder are subfolders summarized by person's name. Such as:
1. /Dropbox/Travel/2021/01/Kevin/
2. /Dropbox/Travel/2021/02/Kevin/
3. /Dropbox/Travel/2021/03/Kevin/
...
7. /Dropbox/Travel/2021/07/Kevin/
With "Smart Folder", users can put all the files under the name "Kevin" in the same Smart Folder "Kevin's Travel Photos". Smart folders are only for gathering files and folders with same criteria, and the original files will still be under each "year/month/Kevin" folder.