The "manage site…" panel has Members -> History of Invitations, which is a "List of pending (not accepted) email invitations". However, the same panel allows invitations to be sent by username instead of email (Members -> Invite members) — but there is no corresponding way to list these invitations that are still pending.

Why not? Could there be? Why do the email invitations get treated differently? Wikidot clearly stores the information, so why can it not be listed?

Also, is there a way to cancel invitations, once made? I'm thinking more about wanting the invitation only to be valid for a certain amount of time (say a month) more so than rectifying mistakes. A manual "cancel" on the list of pending invitations would be ideal — if the list included all pending invitations, not just the emailed ones.