I know it might be a big ask design wise, but further to the request to turn off pinyin on the word review section (and there are good arguments for and against and, also, the formerly advised review options do not apply to every page of the review section when activated and would hinder review functionality even if they did) might it be possible to incorporate a toggle switch, in the default off-position, for each character review page. In that way, a further hint could be provided as required, which for me at least would aid the learning process, tones could be confirmed, and English could also be similarly called up when seeking a meaning clue when trying to recall the pinyin. Of course, you would need to specify each time, perhaps at the toggle switch, whether an English or pinyin answer was required).

After all, you did manage to incorporate the suggested add synonyms feature, and that is an excellent enhancement. I have very little programming knowledge, so this suggestion could well be totally unfeasible.