Leaving Behind the Digital Keys to Financial Lives
nytimes.com
nytimes.com
It would seem a reasonable approach to maintain some 'passwords to passwords' (like: disk encryption, password manager, browser password) and appropriate account identifiers in a sealed envelope (or a digital equivalent), and to put the envelope in a home safe or safe deposit box, or the digital package with one's off-site backups.
This approach implies using 'passwords to passwords' that persist for as long as the package does. Any financial account numbers are likely to be more stable over time.
Managing access to whatever container is yet another layer of turtles.
I'm thinking that storing encrypted files off-site (or in-cloud) and leaving access codes & passwords to both the files' storage and to the contents of the files in a sealed envelope with a trusted person (perhaps an attorney or accountant) would be adequate.