I "love" these projects that won't even describe what they do on their front page or even in their manual. Of course everybody has 30 minutes to spare to try to understand what it is.
The documentation for Home-Manager that is generated is an extremely large html file with every option listed. It is not easy to read or discover options in. The linked tool provides a search field to query the available options for Home-Manager, making it much easier to digest. This is similar to the NixOS Options search tool which does the same job of providing search for NixOS options.