I am unaware of the feature in the Combined View will show whether an Event has sources or does not. Since I do not know which screen (or data) you want to see, I cannot suggest a shortcut.
We may have a Translation confusion. Since you are using the French translated version, perhaps you can post a screen capture? Even it the labels are in French, a user of another language will be able to recognize the view layout.
By the way, an alternative method:
You can create a Custom Filter that finds Events that Do not match having at least one direct source to find Events that need work.
You can also find Event that Do match that rule and Tag them. Tags are visible in many views. So you could spot Event missing that Tag and add sources.