You can do so by opening an issue on GitHub.

You could create a list of steps for anything specific that is missing or for a different build and add it as a comment (or as a new issue) in GitHub so that I will see it and add it to the site.

Or you can of course always fork the repo, add your changes and create a pull request.

It gets saved to the local storage in your browser. So if you are clearing your browser cache make sure not to delete the site data or your checklists will get reset. That also means that if you use a different browser or device nothing will be kept.

They get saved to the local storage in your browser. So if you are clearing your browser cache make sure not to delete the site data or your profiles will get reset. That also means that if you use a different browser or device any profiles that you created in a different device or browser will not be there.

You're probably talking about the game progress checklist. This is a work in progress and I'm adding things. I try to change what is already there as little as possible, but sometimes I have no alternative but to change existing steps. This should stop happening very soon as there isn't much more I plan to add.

I had to pick one order. I tried to pick an order such that even if you wanted to do all questlines, it still makes sense. If you want to ignore some questlines, you have lots more freedom in the order you do things, as Elden Ring is very open ended.