First, amazing app. I’m sorry that the current situation means more cannot review how great your app is for language learning in general. Anyway, some quick suggestions based on my first run through:
Player: If using auto-pause, currently the “D” or Right Arrow skips over non-dialogue portions to the next line. Set an option so D or Left Arrow unpauses only but that clicking during an non-dialogue part skips to the next line.
Font: Likely already on your to do list, but allow users to select their own font for their language(s). The current Japanese one is odd. Tried checking the Chrome settings but does not seem to change it.
Download: Instead of just an Anki export, option to export as a TSV text file.
Print: Add option that allows a H:MM:SS timestamp column (ex: 48:12 “Text from sub”; 1:12:36 “Text from sub”
Anki/MorphMan: Option to link to one’s MorphMan’s known database to use for a number of things. For example “No pause on i+0 lines” would mean a subline that has all known words would play through, while “Hide i+0 lines” would blur them out.
Train MorphMan with LLWN: Instead of depending on Anki, LLWN creates its own MorphMan file (can be imported from Anki of course). Here, users train it by selecting if they know words. Shift+Rclick would toggle from Unknown, Learning, Known.
With a trained morphman, users can have a custom experience tailored to their level. Examples: color words based on their status: green for Unknown, yellow for Learning, white for Known. “Vocab Transliteration” where unknown words have to the user’s native language translation shown above (great for languages close to each other like English/French/Spanish or Japanese/Korean). “Train Comprehension” where it presents words by frequency order and the lines they appear in the vertical view. On top of this, have options as to what LLWN does for words or sentences based on their MorphMan status (blur, color, transliteration yomi, translations transliteration, etc).
Sorry for the suggestion dump, but thought I’d get it out there. Again great job on all of this.