“We can’t afford to lose this person.” Managers love status and insight. If that’s not enough, improvement is not a primary goal, and likely it’s time to move on.

Might work in a startup but senior leadership at enterprisey companies will not accept that as an answer.

They love metrics and that sort of thing, that's why it's hard to quantify even though it's clearly valuable.

Good leaders will help you and can recall instances where your knowledge helped.

Then they can lose two valuable folks. Sucks to be them.

We had a people choice award for such work. And then you could use that in your appraisal.

But yeah, I used to do this just for my own interest of learning. Companies can't accept that only one or two persons are doing this. They would say - its a part of the job.

One thing you can do is keep tab of problems and create a common resource point for all the team. And use some kind of way to show hours saved. Long shot but it holds a substantial promise.

Off the top of my head: how about quantifying it like, "If we didn't have this person, we'd waste X person-hours over the course of the year"? That should help you put a number on it.