Cancelling campaign invitations?

Is this a thing?

Yes you can cancel invites. If you have created a campaign, you can go to the right side of the campaign detail page (there is a blue button with the words Invite players) and click on the invite player button. It will show three things, an email box for email invites, a pending invite list, and a join link that you can copy and paste with. You can cancel specific pending invites there.