This setting is now available in the latest update. Thank you to everyone who suggested it!

I agree, it can easily be an option. I would prefer hiding the sura banners as well in that mode, as it would check memorization of sura ordering (especially for Juz 30).

Ayah marks are helpful for freshly memorized verses as it is useful hint. After it memorization of those ayahs are strong it is perhaps better not to have ayah marks. So this could be a toggle button.

I agree, but also I think I would prefer that hint usually. So please make it as a separate option from hiding the words

Salam! This is a good suggestion, we will discuss internally and consider it.