Adjust Cover ; how where.?

[ohrenkino]

Perhaps it is time to have a look at the "HowTos" and

Actions and batch-operations

How to create a new action? First, create a new action group via Actions > [Actions] Actions or Alt + 6. Then, click on the button [New] New and give your action group an expressive name, e.g., "All tag fields Upper Case". This action group can be applied to the selected files after you have added one or more actions to it. Now, you can create a new action in your action group via the button [New] New and choose the desired action type from the list. At the moment the following action types …

and sometimes even the help helps:

Actions – Mp3tag Documentation