What is the easiest way to take long, complicated notes?

First jot down key points and then take the time to organize it later. The grammar and spelling doesn’t have to be perfect at first, you can always fix it when you organize it.
Separate everything into categories and do bullet points.

For example:
Topic...
1...
a...
b...
2...
a...

Topic 2...

I separate everything into sections. Sometimes color coding helps people understand it better, and it’s worth the extra effort.

I hope this helped :)

Section it off by colors and paraphrase, colors make it easier to remember and when it’s in your own slang and the way you understand it you’re more likely to remember and it’s less to write :)