CPP-Reference in Kdevelop

Hello everyone, I’m working with Kdevelop 5.12.230805. As soon as I hover the mouse over for example cout in the editor, the documentation for “cout” appears in a window. The same works for string, for example. But not for other keywords such as while, return, char, etc.
However, the file cppreference-doc-en-cpp.qch is located under /usr/share/qt5/doc/, as are all other Qt-related files. Solution?
Tnx for an answer!