That's the specified behavior, show only content of site root folder in Site Root node, test folder (in Test files node) and config folder (under Configuration files node). Either you can change site root or in NetBeans switch to Files view (next to Projects where you see the site root) where are all files/folders in project root. So you will see sass, etc...
Note one thing though, NetBeans scan files in Site Root, test folder and config folder. Sometimes it could be useful to "hide" stuff outside of site root to speed up scanning (code completion etc... - if you e.g. have some NodeJS modules for GruntJS you can have them outside of site root) and also hide possible errors coming from them (for instance if some JavaScript framework uses invalid syntax which is however possible with given framework- could happen with some NodeJS modules )