Neat! I'm working on a similar thing but mine is not as far along, and slightly more focused on what I call "subtitled reading" (interleaving source and target language lines of text).
Small UI feedback: the WORD LOOKUP sheet has UI design disease, i.e. imo too much text. I'd drop "WORD LOOKUP" and "CURRENTLY SAVING". Also behind the latter the current word is repeated (it's already the title of the sheet), so I'd drop that too.
Small UI feedback: the WORD LOOKUP sheet has UI design disease, i.e. imo too much text. I'd drop "WORD LOOKUP" and "CURRENTLY SAVING". Also behind the latter the current word is repeated (it's already the title of the sheet), so I'd drop that too.