There are two things here.
There is “Event History” and if you dont have that right on your dashboard or when you go in to your actual device (mine is the floodlight cam) we are looking at different apps because it’s very clear on mine. It’s only when I access that timeline through “event history” from the dahsboard I get the three dots to the right of an event as you describe. When I access “event history” through the device portion of the app, it only has an arrow to the right and it pops up that event as video to view from there, no 3-dot selection.
Then there is what happens when you tap the camera view from the dahsboard (in my case I have only the one floodlight cam, so I dont know what the dahsboard looks like with multiple devices) and it comes up with the camera view live, then you can slide the timeline below the video view to the right, which takes you to previous events and disconnects live view to show you the video of those other events. When you slide out of live, to a previous event, there are 3 dots on the lower right of the screen that become active. There you can delete, favorite/star or select snapshot. I’m not sure how to fine tune this yet, I assume the snapshot is taken wherever you are in the video playback and the favorite/star and delete selection is the entire event rather than a portion where the snapshot is taken.