Does the word "findability" exist in English?
Solution 1:
Anything is a word if people use it. English does not have an authority on what is or isn't a "real" word. Since "findability" does have attestation, it is a word.
This is totally separate from whether it's a good word, of course. But that usually depends on the context in which you plan to use it.
Solution 2:
In 2013, I attended a meeting with my work group. One announcement my boss made was, more or less: OK guys, findability. If you're gonna be away from your desk for more than a half-hour, put a sticky note on your door.