1Password is amazing for this, IMO. My spouse and I have been using 1Password together for more than a decade. One of the first things I set up is a "AAA Read Me First" note with links to a bunch of other notes and documents, including our estate planning stuff.

The biggest thing that makes me stick with 1Password, despite the semi-recent VC shenanigans, is the fact that if for some reason we fall behind on billing (for example, because the credit card got cancelled because I died) the account goes into read only mode forever. As long as 1P is a going concern the data we choose to put there is safe from the biggest risk in our threat model.

Just a year before my dad's stroke, my parents documented every account, password, service they had; it was incredibly helpful after he passed with all the stress and chaos