Take some form of notes. If something is interesting note it. I use pinboard and tag the link with relevant topics so I can get back to it later. Whatever note system you want to use, make sure its searchable. If it's interesting enough, apply it in some form, a mini-program, a essay to your self on why it might be interesting, or some of the other suggestions here.

Finally, if this trouble is new or slowly growing, talk to your doctor...

By applying that knowledge and by teaching it to others.

There's truth in the saying that if you want to become an expert at something you should teach it to someone else. As an experienced software developer there are lots of ways to do this:

- Coach your clients / colleagues.

- Offer professional training and workshops. Training developers in new technologies, techniques and frameworks is a lucrative business.

- Offer non-profit programming classes for children / students.

The question is why would you want to clutter your brain with all those details. If you need an information that you've read about in the past, you already have a head start and know there was something written about that and where to find it. And if you don't need those information in the future, what does it matter that you've forgotten it.

When I'm learning something new I try to take notes by hand or type them up. Every few days I'll rewrite what I learned from memory, as much as I can remember. Then I'll compare my current notes to my previous notes and fill in the gaps that I skipped. I repeat the process every few days until the information is ingrained in my memory.

Use it frequently. Memory patterns form by applying knowledge. Help some open source projects using the topics you learned. Nothing magic.

You have to use it to retain it, imho... and don't be too hard on yourself, if you don't remember it, maybe it was not worth the brain cells...

i think the best memory yet is understanding and visualization. The human brain is really good at visual tasks and if you have noticed understanding really goes hand in hand with visualization.

you acquire long lasting knowledge by doing.

reading only gets you so far.

if you want to retain read knowledge, take notes. what you write down is what you will remember.