How to add existing C/C++ source files in a folder to an existed project?

Sorry for duplicate question: How to add existing C++ source files to the simple "Hello World" project?

And I don't want to edit "root CMakeLists.txt" which CLion use matually!!

But I really want to know why CLion does not support this feature ?

In my oppinion, this is not difficult. Because when you chooes "New CMake Project from Sources" option to create a new project, Clion will add source files automatically.

BUT, the only method to add files for me is delete root CMakeLists.txt and re-import folders、rebuild、reloading、re-waiting :(

Sad T_T