Sharepoint Freamework

Hi. The answer is no. The sppkg file contains minified version of your code files. If you don't have source code, you might not be able to understand which function is which and where exactly you need to modify the code. And the code you write there might break the existing fuctionality due to this. If you have idea where you need to change the code, I would say, after making changes, please test on dev environment first and then deploy it to production or uat.