If your script manager is Tampermonkey, maybe you need to click on trash bin and delete the script from there too, but I'm not sure
You can also click on script, select storage, and make it an empty object, and then save
If this didn't help I assume that the script you're using is writing its data in the website localStorage or something like that. In this case it's might be better to look at the script and what it does so I can give some safe non-destructive advice
I have a script that I want to do a fresh install of, to get rid of the data I entered into it & start fresh, but just deleting the script & reinstalling doesn't get rid of the data. Is there a way to completely wipe the script & data?