I don’t think you missed anything in their documentation. Based on my experience with Cockpit, the main documentation just has the basics covered.
You can do pretty much anything you’d like Cockpit as long as you’re willing to take the time to search the forums, and tinker with your install.
This question is where I found the filter options. I had to tinker with it to suit my needs.
I found that searching for my specific use case will pull up one or two entries that are similar, and then from there I can find the keywords that others have used to describe what I’m looking for. Then searching for the keywords, there’s usually an entry with a pretty in-depth explanation.