The following reports do not have the option to duplicate and edit as custom reports:
Permissions matrix report
This report's parameters are defined each time you run it, so you cannot duplicate and edit it.
Audit report
This report's parameters are defined each time you run it, so you cannot duplicate and edit it.
External sharing report
This report combines three types of objects: site permissions, list permissions, and list item permissions. Due to this, the app is unable to duplicate and edit it.
Workflow report
The report combines two types of objects: list Workflow and site Workflow. Due to this, the app is unable to duplicate and edit it.