Yes, you should see the keyframe outlined with a small empty
circle in it at the bottom if it is done on an empty timeline. If
you do it on a timeline that has something in it that circle will
likely be solid, indicating there is something occupying that frame
(whatever was at the end of the timeline before it).
I don't know/use other method(s) for manipulating timeline
frames. What I always do is right click on a frame and select from
the menu that appears.