Hi,
We chose to use the challenge mode for more "optional" accents, the ones that don't change completely the sound of letters. However the marks you're mentioning haven't been included there since they are almost part of the letter itselfm in the sens that they change the way they sound: We understant that this choice might be frustrating when trying to learn spoken Portuguese, yet it can also be a reminder that the letter sounds idfferently, so it can also be important for spoken Portuguese.
Hoep you enjoy the rest of the program nonetheless,
Regards,
Emilie