When the group is empty it is still displayed, I would assume that empty groups will be hidden.

Now I have half hour searched where the heck is MySQL option set in my cmakelists, then I realized that it is not the option but it is a group.

I'm using this FindMySQL.cmake to find mysqlclient and it creates two advanced options MySQL_INCLUDE_DIRS and MySQL_LIBRARIES, when I uncheck Advanced, then this parent MySQL group is still visible.

Advanced unchecked:

Advanced checked:

You can use that FindMySQL module like this:

find_package(MySQL REQUIRED)
target_link_libraries(library_cmake PRIVATE MySQL::MySQL)