Turns out that the time is editable. But it's hidden by a failed user interface design. See https://experienceleaguecommunities.adobe.com/t5/Adobe-Analytics-Ideas/Don-t-hide-user-actionable-vi...
Feature request: allow the user to set the time when he wants to receive a Scheduled Project's report.
When scheduling a project, the user cannot set the time for the project's delivery. Instead, it will be sent at the time that the schedule has been last saved.
For example, if I setup a Scheduled Project at 2:50pm, the subsequent reports will always be sent at 2:50pm. But that is not the ideal time to receive this reports.
This is a ridiculous workflow because it demands that the user be at his computer, setting up the Scheduled Project, at the time that he expects to receive the reports later on.