Not possible.
The timeline was not a feature in 2013, when this post you bumped is from.Well...You can go to Timescale. On that screen wont show any units and do many screenshot as you like it
I know that, still someone want to know how to hide units on the map. CK2 have that option EU4 not.The timeline was not a feature in 2013, when this post you bumped is from.