What did you do today?
What do you need help with?
What went well?
What was frustrating?
What should we change or fix?
When we get together to talk about their day or their week, these logs are extremely useful. Sometimes they generate tickets, sometimes book or course recommendations, people to talk to, sometimes just conversations.
I had a good mentor when I was doing sysadmin. Not quite as formal as this, but the conversations were similar.
I used to track my tasks in Jira with the thought that maybe my boss would look at it and see what I was doing. Of course he wasn't looking at it so I stopped doing it.
My log is mostly for me to provide a list of achievements to my boss whenever there's a review, or if I'm questioned about what I spend my time on.
If I sysadmin again, I am going to do that. "Why those trains ran on time."
It’s one of those things that would probably be naturally suited to voice-activated systems (“Hey Siri, today I updated system X to avoid Y, and I wrote a script to improve process Z on input A” - 5 seconds to say, log saved in the right place, keywords like “updated” and “system X” recognised and formalized into some record, etc), if only such systems actually worked on any word beyond the most trivial (good luck with context-less mentions of pythons, rubies, native-american tribes who somehow serve pages of webs, androids in phones, etc etc).
Installed update X to prevent risk Y
Wrote script to advance process Z on input A
Etc...