If you delete the sheet name altogether (click to edit, then delete all characters and leave it blank), then RB will automatically assign a unique sheet name upon export.
The other option is to create a unique sheet name using syntax and loop iteration values. In order to use syntax in the sheet name, you enclose the syntax in curly braces. And an example of a loop iteration value is @label. So here’s an example of what you could use for the sheet name:
The above would use the label of the loop instance as the sheet name. Just keep in mind that names in Excel have restrictions on length and don’t allow certain special characters – so you’ll probably want to keep the labels simple and short.