Save it encrypted on an external USB-drive if you only have one drive in your box.

1. Of course you can buy one.
2. you can also buy a sleeve, ram an old disk in there, plug it in, and voila,

now you can create an encrypted drive and if you are a bit more safeguarding: create a hidden volume/container in there. Double Whammy.

So, what about remembering passwords and stuff ....

Well, you could use an innocuous key file with stenography in it.

Or you could use a browser extension as a password manager. Also very nice to sync it between devices .... DON'T DO IT!

Use keypassxc, and if you must use it on a handheld: hardsync it over the wire. -less is in deed care-less.