I am developing an Ubuntu Phone application "QML app with C++ plugin (cmake)" but I have so many qml files so I want to separate them by functionality

ApplicationName

    CMakeListes.txt
    ..
    app
        CmakeListes.txt
        ApplicationName.desktop.in
        tests
        mainComponents
            sub directories of mainComponents
                some files
            some other files
        ApplicationName.qml
    po
        CMakeListes.txt
    ApplicationName.apparmor
    manifest.json.in

but the "mainComponents" folder dose not appear in the project tree and after some searches I found that I must add CMakeListes.txt in every new folder and this:

add_subdirectory(folder_name)

instruction in the parent folder CMakeListes.txt file but I don't if there is more to add and I don't know how to create the CMakeListes.txt

thanks