On the "My Requests" list, the actions available include the "edit" function. However, in the Request Detail page it is missing. How do I edit from there?
The edit button only appears for requests that are at particular stages of the request lifecycle - the ones without it are in the fulfilment range, where any approvers involved have already examined the requests and passed it on for fulfilment.
Information can be edited, but there's no specific "Edit" button - clicking on Fulfil will take the user to the edit screen where the status can also be edited. If a user doesn't want to change the status but instead edit the request definition, then clicking the Save button will keep these changes without performing fulfilment. The same goes for a request in the Approval range - the Approve/Reject button does this.
The reason for this is to stop a user editing their own request after it's submitted; only the approver or fulfiller can correct any issues as part of their change.