One time scheduling links explained
One time scheduling links are created when you use Front Calendar to insert calendar availability directly into emails. Since that scheduling link is only being used for a single meeting and typically won't be re-used in the future, it will be hidden by default in the "Scheduling Links" page of Front Calendar:
Hiding one-time scheduling links gives you faster access to the scheduling links you re-use frequently and prevents your list of links from becoming cluttered. If you ever need to view your one-time scheduling links, simply uncheck the box next to "Hide one-time scheduling links".