Search with CKAN metapackages
If you use the CKAN mod manager then you can use a file that it automatically generates to tell KerbalX what mods you have installed.
Go into your KSP directory and into the CKAN folder.
installed-default.ckan file and drag it onto the mod search section. KerbalX will then find craft that will work with your installed mods. (You can do this with any .ckan metapackage file.)