1. Have a complete MinGW/gdb Kit configured in Creator and have MSVC with cdb installed.
2. Go to "Tools" -> "Options..." -> "Build & Run" -> "Kits".
3. Select the MinGW kit.
4. Change the Compiler of the kit to an MSVC compiler and change the Debugger Engine to cdb.
5. Click "Auto detect".
   Creator will change the Debugger Engine back to gdb and set a path to a gdb executable.
6. Change the Debugger Engine to cdb again.
7. Click "Apply".
8. Click "Auto detect".
   Creator will now set a path to a cdb executable.

The second behavior is correct. When "CDB Engine" is selected, "Auto detect" should always set a path to a cdb executable. It should not matter whether changes are already applied or not.