simply amend the Title of your action in process designer. Then you will have an "Add Attachment" action but the user will see the "Resolve with Attachment" instead of the default Title. This will also work if your "Add Attachment" is in your status as optional action. But be aware, that you only can have one "Add Attachment" action on one status, no matter what the title is.
- Open the Process Designer.
- Stop your process.
- See Screenshot
- Save process and activate it again.
Otherwise it is not possible to add two actions of the same type to any collection. You can only have one of the type add related, and so on.