This idea is similar to when you perform an internet search and the hyperlinks change from blue to purple after you click them. Multiple users have requested that map features be able to do something similar, like adding a slight halo or other subtle symbology change to show that a feature has already been clicked on.
For example, we operate several data-intensive websites where users research dozens of features per visit. It's easy to keep clicking on the same features, which wastes time and increases frustration. I temporarily recommended using the Draw widget to mark features, but the features drawn only persist for that user session.
This functionality might be nice as a widget so users could turn it on/off or even "reset."
