I am trying to modify a "view" for donations, so that I can see the Primary Campaign Source. When I clicked "Edit" to edit the view, I don't see campaign in the list of fields.
Is this possible?
Campaign field is not available for display in Opportunity (Donation) views. There's a feature request on the Salesforce IdeaExchange to make this field available, so I recommend voting for that.
As a work-around in the meantime, you could create a custom formula field called
Campaign Name, and display that instead.