I do need QT_QML_DEBUG for qml debugging. Because this is still so random, when the flag actually get's applied, I wanted to force enable it in my CMakePresets.json for debug and relwithdebinfo. Now it looks like that QtC catches this flag (see video) and removes it. It does not to set `QML debugging and profiling:` to enabled. I had to Build->Clear CMake configuration and then Build -> Rescan Project for it to even the popup with Apply configuration changes? Did not help.

qtcreator_cvsgwFvODS.mp4