This is the article about keeping an epigraph journal:

https://writingcooperative.com/why-every-writer-should-have-an-epigraph-journal-5f080a736ed7

I use Evernote, and have a notebook there just for this purpose. I make a new note for each book I'm reading or podcast I'm listening to, and write down key quotes or ideas that resonate with me.

After reading your article, I'm now going to start each note with what I specifically want to get out of the book or podcast - the reason for reading or listening to it - before I even start.