See what's new in Calamari
From now on, you can block time-off requests from people designated as substitutes.
Why? To ensure that someone is always present. When someone is assigned as a substitute, that person will not be able to take time off during the same period.
The new restriction works in two modes:
Try it: Go to Configuration → Absence types / Time-off categories → [select absence type] → Restrictions → Add new rule: Requester cannot request time off for a period in which they are assigned as a substitute.