Hello Uma
Kindly refer the below link:
Message settings in QM | SCN- Hopefully it would be helpful.
Also to add on there is no standard node in QM, however if you go to SE91 and enter message class as QP then search where used list by selecting the program option you will find a program where it is being used as a message class.
Now if you want to deactivate it then you have take the help of an ABAPer. Since it is a standard program, I am afraid that system may ask for a access key.
Regards