Qt Creator doesn't add new files to CMake project

After creating a cmake project following [the process listed in Qt Creator's docs](https://doc-snapshots.qt.io/qtcreator-4.0/creator-project-cmake.html#creating-cmake-projects) the user manages to create a cmake project. However, when a user tries to add a new source file to the project by right-clicking the tree entries listed in the project folder, all options are disabled/greyed out. Here's a screenshot of the right-click menu.

However, although the file creation entries available through the right-click menu are all disabled, the same options are enabled in Qt Creator's "File" menu, as can be seen in the following screenshot.

In spite of the file creation options being available through the "File" menu, if a new class is created throught Qt Creator's new class dialog the CMake project is not updated to include the newly created files.