Not parent, but I can chime in with my current system: Simple logs that I can search and copy.
The key for me is that it's not about the format. The format changes with the context: I have a different logging strategy for fitness(Fitnotes app, and since I was just gifted one this past week, a Fitbit) from the logging used for programming notes(repetitive short block comments with date, time, and sometimes title). I have a generic diary text file that contains catch-all musings, but I am increasingly using different logs for different tasks since I don't currently face a lot of time contention that would necessitate a detailed calendar.
My logs are not just what happened but also what I wanted to happen on that date. I'll often copy-paste the same to-do list when I didn't finish it that day, or "redraft" the same thought an hour after I first logged it, with some elaborations. Keeping it around, I learn what is or isn't working at a glance by skimming over these repeats hours to months later.
Having the date and time is essential to this because it makes the log a progression: my recent activity is my most important, most of the time, and so in the case of the programming logs, I can gradually edit and eliminate them as the code changes and the momentary thoughts of "I need to do this next" grow irrelevant, while if it's something like a log of weight/reps/sets, I just want to copy, increment the numbers a little higher, and add a note about anything weird that day that may have made me change plans.
When I really need freeform notes I will turn to paper, and I can see bullet journaling techniques being worth trying in the future for adding some structure to those. As long as I have dates I can usually recreate the context of any particular note, though.
Something I just thought of: is there a browser extension that would automate logging my history when I want to research something? That's a pretty common task that I currently address manually with a lot of right clicks and ctrl+C's.