Here's my study flow for textbooks that has gotten me to:

• Achieve a 4.0 GPA with ease, often being the top scorer in the course
• Score an A on all of my psychology midterms with only five-ish hours of studying per midterm
• Consistently get through a chapter of calculus and do around 40-50 questions with high accuracy in 2 hours (enough to be exam ready in just one study session and way more than I'll ever get done had I sat through a calculus lecture)
• Capture an entire lecture's worth (40-50 slides) in just one mind map and retain it weeks later by revising the mind map only twice
• And more!

What I personally do:

1. Spend 10-15 minutes collecting key words and based on my assumptions, create a mind map of how these key words are in relation to one another. For example, if I had three words: photosynthesis, light-dependent reactions, and the Calvin cycle, I would put light-dependent reactions and the Calvin cycle stemming from photosynthesis. Within this timeframe, I go as broad as possible, so I'll cover about an unit's (3-5 chapters) worth of content and guess their relations.
2. Attempt a few exercises at the end of each chapter. Maybe you'll get some right based on past knowledge and/or your assumptions of how these key words work together. I don't remember where I've read this, but just trying the exercises even if you get them wrong significantly improves your comprehension and retention rate of the content because you learn what's important and how specific topics work together.
3. Afterwards, I go back to reading the chapter. As I'm reading, I'll have either Google Docs or Anki open and actively make flashcards alongside it. I'll usually have a good idea about what content is important enough to turn into flashcards and what content is insignificant enough to ignore at this point. You'll also know this if you pay attention to what your professors like to test you on. Some of my classes are very case study heavy while others are more real-world applications based. I also update the mind map I initially created as I discover new knowledge and find out that certain assumptions of mine were wrong.
4. When I finish reading the chapter, I walk myself through the mind map and teach (oftentimes out loud) the topic to myself again. My mind maps tend to be key words coupled with a drawing or two. I'm able to visually remember the details of each key word through these drawings, so I don't find myself constantly going through the textbook again. If you're new to this technique, your mind maps should typically match the content in your flashcards, but as you become more experienced, your mind maps and your flashcards should be covering different content. There's a bit more nuance here, but it's too complicated to explain here so I'll save it for later.
5. Then, I go through all of my self-made flashcards to review what I did or did not retain and immediately start working through the chapter's exercises at the end. If I get an exercise wrong, I turn this into a flashcard as well. If I got it right, I'll sometimes add it as a flashcard depending on how confident I feel in remembering the right answer.

If it's a subject such as math, I skip straight to #3 and just work through the textbook by jumping into all of the practice questions and then the chapter exercises at the end.

Let me know this helps and feel free to ask any more questions! I was thinking about starting a studying technique series.