Am not sure of this custom style-sheet and JavaScript section. Might be they would've customized the page properties as i too don't find them in CQ 5.4 / 5.5.
Though you may not be able to include your custom CSS and JS in JSP using <cq:includeClientLibs>
, you can make them as part of the clientlibs that is getting included in the form or the page component.
i.e. You can create a cq:clientLibrary folder that has the categories property set to the same value which is being included in the page.
But, it is recommended to be cautious while trying this way, as your JS would be available in all the pages where this client library is included, and hence try to write the script as specific as possible so that it doesn't affect the rest of the functionality.