you can't edit an hex file so, what you have to do is edit the code and program it you can find exemple code in the Psoc creator exemple code.
If you already have the hex file of the reference design, here is what you can do:
1.Open EZ-PD Configuration Utility, choose "Read From Firmware File" in the File Tab, and open your hex file.
2. Modify the PDOs to the value you want, like disabling 20V/2.25A and change 15V/3A to 10V/3A.
3. Choose "Save From Firmware File" in the File Tab, save the configuration table to your hex file.