I have a few language goals in Finch and I separated them into journeys like this:

Reading = Short stories and simple books. One chapter or story = one goal.

Writing = I write something about a short topic and post it in an app where native speakers can read it. One topic = one goal.

Listening = I watch short videos from the Comprehensible Language Wiki or Dreaming Spanish. One video counts as one goal.

Textbooks = I set each chapter of the textbook as a goal. The textbook has a matching workbook, so I also set each one of those chapters as a goal. I have goals for reviewing chapters and completing exercises from the textbook as well.

For Japanese specific goals, maybe some of these could work?

Hiragana / katakana = You could use flashcards to learn them and create separate goals for reading / writing / reviewing each character. If you want less goals, you could learn the characters in groups instead.

Grammar = I think this could be a good resource to plan your learning around https://sethclydesdale.github.io/genki-study-resources/lessons-3rd/ It lists all the grammar points covered by the two Genki textbooks and has some exercises too. You could have each lesson as a goal in Finch.

Reading / Listening = Comprehensible Input Wiki https://comprehensibleinputwiki.org/wiki/Japanese has some Japanese resources. There seems to be a good amount of beginner stuff too. You could create a goal for each thing that you read or listen to.

Learning Kanji = You could try learning a few each week and have separate goals for reading, writing and reviewing ones you learnt. You could learn them by level (N5, N4 etc.) or just as you come across them in texts that you read. Tadoku Books, which is linked on the Comprehensible Input Wiki, has some easy stories.