Org mode.
I don't worry too much about the structure. So long as it's written down and backed up, it is searchable, and that's enough.
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At the end of the day some of this information is most likely lodged in your brain and the digital version can be discarded. However some of it should be retained manually in some system - or at least I feel it should.
What approaches do people use to consolidate and store this information to allow all tabs etc to be closed for the next work day?
I don't worry too much about the structure. So long as it's written down and backed up, it is searchable, and that's enough.
One file is just a time-ordered log where I put loose observations. Then for specific projects/themes I have separate files.
It is a bit of a mess, but it doesn't matter. It's a sort-of append only log.