Disclosure: I am a founder at bytebase.io, currently in closed beta. We're building Bytebase with this kind of use case in mind.

Wikis - we found wikis are too heavyweight and formal to be used consistently for recording learnings.

Slack - in our experience, Slack makes capturing learnings easy but organizing and keeping track of learnings difficult.

Our goal with BB is to make recording a learning as convenient as writing a Slack message AND to make organizing and keeping track of these learnings similarly easy.

You can write bytes directly in Bytebase or save them from Slack.

Would love any feedback or ideas. Email me (cara@bytebase.io) to get access to the closed beta with HN in the subject line.