You mention not wanting to "compile everything under the sun in a Microsoft Word or type everything in Latex", but I think doing something similar to this may be helpful.
Here's what I have started doing and it's been very helpful for me over the past year or so as I've been learning a new field:
I am a PhD student in biology and am an aspiring teuthologist (the study of octopuses, squids, cuttlefishes, etc.). I have started to jot down everything I want to remember from the papers I've read. Not every detail, but just the things I want to have in my working memory and be able to recall in the future.
The key for me is organization so that I don't just have endless bullet points, or paragraphs. I use LyX and break up my thoughts into Parts, Chapters, Sections, Subsections, Subsubsections, etc.
Everything I want to remember in my field has to have a place. If I learn something completely novel, I just create a new heading and file that thought in place. I'm writing it akin to a book or journal article, so every fact or idea has a reference where I got it from. I also screenshot good figures and add them.
Here's my table of contents as it currently stands to give you an idea of where I am about a year in:
Table of Contents
It sounds like you may be in mathematics so it may take some creativity to see a parallel.
What I find so helpful about this approach is:
- Each new bit of information I learn and want to remember fits into an organized framework.
- When I learn something new, I'm forced to think through how it fits into my existing knowledge framework when I decide where to write about it.
- Because it's broken down so finely, I can easily find information I want to brush up on and only read a paragraph or two to recollect all my past knowledge that has gotten fuzzy.
- Because it's written by me, my brain often slides back into the clarity I had when writing a particular section. Especially helpful when I'm looking back at a topic I haven't examined in awhile and everything is foggy.
- I've chosen what I want to remember so I am never filtering through irrelevant details.
- Everything has a reference attached, so if I want those details I know which paper to find them in.
- As I'm adding new information in a section, I'm forced to interact with relevant past knowledge, which helps integrate ideas and synthesize main concepts.
- If a colleague or future student wants to learn something quickly, I can give them this "Reader's Digest" version.
- I can create a section and leave it empty to remind myself I want to learn about that topic in the future
For full disclosure: the downsides
- Organization is required. You can't get too lazy and just throw info anywhere.
- Sometimes I have to put the same information in multiple places from different perspectives. e.g. if I learn about octopus brain physiology, then that info could go under the octopus biology heading with a subsection on brain physiology or under the brain physiology heading with a subsection on octopuses. Sometimes this is helpful though, because I see how the same info tells me something different from different perspectives.
Since this post is getting too long for anybody to bother reading, I think I'll stop it here. I hope someone else finds this method as helpful as I do! Plus maybe one day you will have a whole book written and you can publish it!