You have the option to change/delete a saved report in the tool by following the instructions below:
You log into the tool and click on the report symbol in the survey you want to work with (first symbol to the right from the language flag)
You click on the button save & load
Afterwards, you click on the button manage report. Here you can find all of your saved reports of the survey with possible filter and series.
You can click on the trash can symbol to delete the report in question.