I primarily added Anki cards from Obsidian. I'd have a heirarchal note structure for the subject (e.g. physics -> paper 3 -> astrophysics -> stars -> star type categories). Then I'd have my plainly-formatted notes, and below it I'd have some flashcards. The Obsidian4Anki extension let me create cards from the markdown.

The cards would strictly be on the topic in the note, generally be written around the same time or a few days later, and would be Q-and-A or clozes.

So as an example, "What colour is an O class star::Blue" would be in my notes and turned into a matching card, or "A {1:type 1A supernova} always has an {2:absolute magnitude} of {3:-19.3}" would create three cloze cards.

At the top of each note I'd use a note property to specify the notes' place in the Anki heirarchy, and I'd use the first three parts of the Obsidian heirarchy. So I'd save it as Physics -> Paper 3 -> Astrophysics -> [many, many cards]. I always duplicated notes to make new ones, so I rarely touched this.

Generally I'd practice all the physics cards at once, but categorising them this way let me drop the paper 1 cards once I'd done it and focus on paper 2 and 3 etc.

Honestly, though, I first started this when I was fourteen. My notes and my Anki decks were a complete mess compared to when I stopped when I left school four years later. You'll find what works for you - and clean things up - as you go along.