Go to ADS DBA-Tools option -> MySQL->Instance Manager-> Select registered  MySQL database from list-> In variables tab no short cut is provided for setting variables, now click on Set Variable Icon ( Last icon on Right Side), it will open window for setting variables.

Now  Go to Instance Manager of any other DB you will observe that there we have "Edit Server Parameter" Icon as well as Short cut on Right Click.

I think we should provide the same in MySQL as well for maintaining uniformity.