On a file path, we can see a little star next to the name of a file. Tooltip says it’s for marking it as favorite. Once it’s done, tooltip says it’s marked as favorite.
The favorite files can only be found in the search bar results. It's not even possible to see all favorited files because at best, the search bar results display around 20 results.
It's a remnant of Sonar, at that point in time, you could define a widget which would list all your favorite files in a table, and put that widget on a dashboard.
It's no longer useful and should be dropped.