On the left sidebar you can select to show the History. This appears to be a list of any person that you click on to select them from the Person Index, or in one of the views in the main part of the screen or through RootsMagic Explorer.
One other user interface place that should add to the History sidebar is the FamilySearch Person Tools where you are processing the list of people who have changes. Once you have processed a person, they disappear from the Person Tools sidebar and, unless you took notes, there is no way to go back and figure out who it was that you worked on a moment ago.
The reason this came up is that I figured out on person #4 that RM was no longer showing me the Sources associated with a person, but by then I had no way to go back and figure out which were persons #1, #2 and #3 who I should re-check.
I posted another topic here about the problem with Sources.