Ask HN: How does your organization document experiences?

I am in a volunteer-based organization and we are doing a lot of things, but as you can imagine because of all the volunteering, people constantly join and leave. Right now, when someone leaves, unfortunately they take what they have learned with them. They may leave a document behind, but we have found it cumbersome and unscalable to go through all of them. So far, for repetitive tasks we have found checklists to be useful, but for other things I am looking for some system that:

* can be used to record variety of validated experiences (example: unsuccessful projects)

* does not take a lot of time from the newcomers and the rest of us to grasp them

* are organizable/filterable based on the activity, keywords, or dates

I am not necessarily looking to add another software to our stack, ideas about how we can use the typical tools (docs,sheets,trello,etc.) would be preferred.

I would appreciate any comments you may have, it may save a lot of volunteers' time. Thanks