Also using my password manager, keepass2 in my case (synced over webdav). A password manager should provide plenty of options to structurize. Password database is a part of scheduled backups, and always present on multiple synced devices, so a total loss is hardly imaginable.

As SSH keys were also touched as a topic in the OP, I just wanted to add I just found that there seems to be an addon for keepass that makes handling those even easier: lechnology.com/software/keeagent/ (haven’t tried that yet).