I can't say this is an official answer, but here's what I'd do. When wanting to be added to a Trusted list, I look at the profile page of the Profile Manager. I click on the link to their Contributions. This displays a dated list of when they last made any changes. If their last change was over a year ago, then I'd send a request to email@example.com requesting to be added to the Trusted List of a page with an inactive profile manager.
Be sure to include how you're related to the profile in question.