Hi, and welcome to the forums. I wanted to reach out to you because it looks like our need for Anki converges here, as I also study NT Greek vocabulary. Your mention of vocabulary by frequency makes me think of the frequency lists in Metzger’s Lexical Aids which I have been using for years. Are you also using Metzger?
Anyway, I can share what I have, or at least the set up to get you going. Here is a screenshot of one of my cards (with the answer side showing):
As you can see, I have built this card type around Metzger’s vocabulary lists, although I also include other words as needed (which would be those fewer than 10 times in the New Testament). The note type will generate cards for both Greek first and English first, thus two cards per vocab note.
If you are just getting started, I could share some of this with you so you could take it from there. As for organization, your needs are a little different than mine: I just have all of my vocabulary in a single deck (I also have another deck for grammar matters, including a lot of conjugation stuff). Since you want to sort by frequency and also by the New Testament book, then here are my recommendations.
Let’s start with New Testament book: each vocabulary item in most cases would appear in more than one book. Because of that, subdecks are not the way to go, because then each card would have to be duplicated to each subdeck, and those copies would function independently from each other, and so you would not achieve your goal #3 in the original post. Instead, this is a case for tags. You can tag each vocabulary card with a tag for each book the word appears in. When it comes to learning the cards, I normally would recommend you do not worry about which book of the Bible the word appears in. Rather, once a term is learned, allow Anki to keep presenting it according to its schedule so that you never get a chance to forget it. However, there may well be times when reviewing the terms in a particular book would be useful to you, and that is where the tags will come in handy. Since you would have tagged your cards by book, you can set up a custom study by tag so you can review cards by book for the extra review.
Now comes frequency. On the notes as I have set them up, the frequency is one of the fields, so that information is already encoded in each card. It would be possible to create filtered decks based on the content of that field in a similar way to the tags I described above, but it might not be a convenient an approach if you do need to have them regularly separated into separate decks. If such is the case, I think that is where you would want to use subdecks: one Greek Vocab parent deck and one subdeck for each frequency group.
My preference, as I mentioned before, is to have all the vocab in one deck, and then I manage which cards to learn next mostly by the order I added the cards. Since it is a massive undertaking to add all of the cards, I mostly add them as needed—in case you are curious, I chose to start from the least frequent, since I am reviewing from my studies from 15 to 20 years ago, and it is the less common words that I do not remember as well and slow me down in reading from the Greek. Also, I have been simultaneously going through my Greek grammar book, and I add vocabulary from each lesson, so the order is a little odd, but I will eventually get all of them. But anyway, my point is that you don’t need separate decks or subdecks to manage when you learn something. You can set that with the learning order (it is the Reposition command in the Browse screen), or even simply suspend cards that you want to save for later but are not yet ready for.
I hope that helps. I may be of further use to you, depending on your needs. For example, do you have the Metzger book, and would you like to have the cards that I have made so far? Or perhaps I can help you adapt my solution for your needs. Just let me know.
Years ago, we used to study the Metzger frequency lists by PowerPoint. Each group of frequency was a separate PowerPoint presentation, and we would run through the slides as though they were flash cards. It was a great solution at the time. Yet Anki is so much better for several reasons, especially the scheduling based on performance, which PowerPoint was never designed to do. I think Anki is the best possible platform for this kind of thing, especially as it is so powerful in allowing a very great degree of flexibility to be tailored to the particular needs of the material and one’s own preferences. If you are just getting started with Anki, I hope you will soon find it as helpful for you as it has been for me and so many others. If not, let us help you getting working for you.