Είναι πολύ καλή ερώτηση! As Sean said, we started with the course already defined, it already had 1692 words in it. Although called (originally) “1692 most important words in Greek”, they are in fact not the 1692 most important words in Greek. It’s a long story. But, we had so many users/learners enrolled it seemed a better use of our time to try to fix what we had and then just keep adding to it. When we started there were no articles, sound, context examples, etc. What it had going for it was a lot of users. So, we went through the entire course and added all that material. People kept asking about word frequency, etc., but as has been mentioned the structure is what it is, and the ordering cannot be changed. Besides even if it were possible people keep arguing about the order, and there was for a while endless complaints about words that some didn’t consider important. See @spdl79 comment above for the inside joke:
to which I always reply “every word is important”, sometimes followed by “if you don’t want to learn it, then don’t”. There is a way in Memrise to suppress words you might think are useless to you. But I’ll bet you that if you read Χάρι Πότερ ( Χάρι Πότερ - Βικιπαίδεια ) in Greek, you’ll need to know κλεψύδρα!
So, to address your actual question, at least for my part I just keep adding batches of basic that I know or am learning that I find are not in the course. I continued to be horrified at how many basic words aren’t here (yet)! Sean recently dumped a course that he’s been working on and gave it to me and I’ve been adding for the past few days. It’s a long slow process, even when have a list of words. You have to create an Alt for all the Greek nouns and adjectives because we want to present every noun with its article, but not require that for testing, hence an Alt is required. We also want all adjective forms available as valid answers when testing, so we have masculine shown, with feminine and neuter as Alts. If the words have several meanings and many certainly do, then an Alt is required for each “other” meaning. Then I look them up in Lexilogos or Glosbe and make sure the genders are correct, they’re not always obvious. Then I get the audio pronunciation from Forvo and if necessary, doctor up the sound if it is poor. Finally I look for a context sentence in either Lexilogos or Glosbe. You can see how it easily takes an hour or more just to do a single Level. What we’re all looking for is quality, the course used to be frankly pretty crappy, people were complaining all the time, the original author never replied to a single comment on inquiry.
So, now, if you want to provide lists of words that you know aren’t in the course (see my previous comments), then please by all means. They can be any words that as a learner you want to know. That’s what I do, taking words from my weekly lessons, from the texts I’m using and from notes I’ve taken. I keep asking myself “well why isn’t this words in the course?” Of course, this is rhetorical. There is no answer to that question. If you really want to learn a bit about why the 1692 are what they are, I suggest you visit Harry Foundalis’ web site: Greek Language This is where the original list came from. Apparently Harry thought these the most important words, but as you by now are learning, the list is almost endless! As I mentioned to Sean in another post I’ll have an MS Word version (or maybe Excel) available of all the words in the course soon and am more than happy to provide it to anyone who wants it. One caveat to the list is that it only lists the primary Greek and primary English version of the words, there is no way to dump all of the Alts. Sadly there doesn’t seem to be any kind of database export function 
