Yes, this is extremely common, both as a continuity means and/or as a localized password manager. Know someone who uses a Rolodex for hers, which is funny and yet it works.

Doesn't work well in office environments, but at home the local threat model is largely fine with this.

Yes. Old people constantly do it, since they have no hope of remembering 15 passwords. Sometimes, they can barely remember 1 (one).

I've written down one: the master password for my Keepass database, along with instructions on how to get to and open that file. It's in a 'open if I'm no longer alive' envelope.

It is absolutely a thing people do. Google even offers a convenient printout as a way to provide account recovery.

> Is writing down passwords something people do?

Yes, it's pretty common.

The passphrase to my bitwarden database is in my will. And a bitlocker decryption key is right beside it.

It is what the vast majority of people do.