We’re on 10.1.400.28, and in Report Style Maintenance we see :
Selecting a Report Style ( here, the third one ) and clicking on the ‘X’ in the ToolBar ( circled in Red ) will delete that Report Style.
You may have to recreate the Report Data Definition used by the Report Style before you can delete the Report Style. If you do, it doesn’t have to actually work - the RDD just has to have the same name as that in the Report Style. Just make a new RDD, copied from the Base RDD, with the name shown in the Report Style Data Definition Field.
Then log out and back into Epicor after creating the temporary RDD, and try to delete the Report Style.
After you delete the Report Style, then delete that temporary RDD.