I have found for myself that there is a lack of vocabulary learning apps that have good search functions. When I make a search function, I want it to be able to find all subsets of words, that I could think of. Instead what many search functions only allow you to do is, to first find one set of words, and then in a new separate search find another set of words. Currently working on that search function.
Also what I find annoying in spaced repetition learning apps I have seen so far is, that they will ask you very simple words over and over again, just because you didn't see them in a while. But I really don't need to learn those words over and over again, because I just know them.
Another annoying thing is, that in some apps you cannot see your learning progress. How many percent you already learned. Or that you cannot specify how difficult a word is to learn. Or how relevant it is. All this metadata, that could be good for learners to be able to search through, when searching for the subset of words they want to learn next. Oh, and of course tags ... With tags one can add all kinds of attributes to words. Maybe I am only looking for nouns or verbs. Maybe I am only interested in words that have something to do with family.
There is still a lot to do, but it is taking shape nicely.
The app is written in Python and tkinter. It is very simple to use in most aspects, and I really don't care much about the looks. I actually find them refreshingly simple and functional. Not this "everything flat" kind of epidemic in UI, and widgets still give feedback when using them. Not web based with the typical nodejs or npm overhead and tens or hundreds of dependencies. Nope, keeping it very minimal so far.
I also have another idea, that might give it a modern touch, but that might also introduce overhead and probably should be an optional setup or feature: Give users tools to let LLMs generate example usages of words, if they want to do so. Of course that would have to be a local LLM I don't want to get into users having to sign up somewhere and get API keys and all that.
I am also not planning to make a mobile app. Maybe later I can create an API, so that one could build a web frontend, if one chooses to do so. But first I want to build this app and the functionality behind it.