Pasta water is in fact an excellent thing to save… As a cooking ingredient.
Specifically, what you can do is freeze it in an ice cube tray, and then store the cubes in a Ziploc. A handful of cubes added to a soup, stew, stock or sauce will give it a smoother, more silky texture thanks to all the starch.
Seafile store data in its own proprietary format. There’s no way to just go into the disk and browse the data. You need a proper backup solution.
In my case, I sync all my Seafile data between my server, laptop and desktop, so in the worst case I only lose the file history. A better option, if you have space, is to backup the Seafile storage volumes as well.
Seafile provides ready made compose files, with a detailed guide - https://manual.seafile.com/11.0/docker/deploy_seafile_with_docker/
Also, note that if you make an account on their site, you can get a free pro license for up to three accounts.