I am having trouble figuring out how to remove collaborators that have already been deleted from the account from showing up in drop-down menus (field type = collaborator) when assigning projects. We only have 3 active users on the Team, but all the old team members over the past 4 years that have been removed from the account still show up in the drop-down menus when assigning projects. How do I remove them?
Change the collaborator field to a single line text field. Then convert it back to a collaborator field.
Are there any projects (including old projects) still assigned to any of the old team members? If so, do you need to retain that information? If you need to retain that info, you may need to put up with seeing them in the list.