There is a clue in the name - ChessBase Reader 2017.
There are more clues in the Chessbase link you gave:
With the free ChessBase reader, you can open all standard file formats (.cbh, .cbf, .pgn), play through games on a stunningly rendered board, watch ChessBase training videos and much more
No mention of writing. If you could modify games with this then ...
Upload a PGN and then you play the computer interactively. You play moves from your repertoire and the computer plays the opponent moves. This is also open source.
Similar functionality in the "Opening Trainer." The interface is a bit different but it tracks what lines you have learned a bit differently which is nice.
You can try chessable.com, it is possible to create your own course by importing pgns. The spaced repetition software will then test you on the variations in the pgn the same as the purchasable courses from other authors.
After signing in to the website open the drop down menu and select 'Create a Course' then follow the instructions.
I believe it isn't 100% ...