This might be against the grain here but I prefer simply to practice remembering things well, like humans did before writing was invented. Its hard but worth attempting. I usually engage in the thought for a while, thoroughly milk it by letting the mind wander wherever it pleases, and it typically stays etched. This has worked for a long time now.

I am someone who despises the modern human reliance on technology for just about everything, which IMO is weakening our abilities, be it innate or cultured, and I have been on an extended detox. Given that writing is one of the most pervasive technology ever invented, I am shunning it as well as much as possible. Now, in modern society, writing as a means of knowledge transfer, and thus reading, is inevitable, but it need not consume us and make us its slave is what I am saying. For instance, I do all the private software architecture design in my head and rarely use the large whiteboard on my home study wall. But that technology is so ingrained that I, like most people, involuntarily visualize written things even when just using my mind to engage in ideas. I just can't imagine how it would have been had humans never invented writing. I mean not just related to tech, which probably wouldn't have existed as we know it, but in general.

All that said, the only problem for me is wrt music. Quite frequently I generate beautiful melodies in my mind that I engage by humming, but quite often I lose them after half an hour of other activity. So I preemptively use my cell phone to record the melodies to work on them later. I kid you not, when I browse the list occasionally, there are many in my list from years ago that I don't at all remember had occurred to me. And even after listening multiple times, apart form a few melodies, I forget most of what I hear. It has baffled me no end. I will crack this case one of these days.