For some types of bookings, you may need several employees or one employee and one room. To add multiple resources (rooms, employees, equipment, etc.) to a single booking, you can either predefine them as a service, or create them manually.
You can find out how to create a service with predefined dependencies for several resources here: Create dependencies between multiple resources
Of course you can also add one or more resources when creating a new appointment. Click on an empty space in your calendar and create a new appointment. In the resources area of the appointment window you can then for example add more employees. Either select the corresponding resource in the drop-down menu or use the search function in the field by typing in the name of the resource.
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The appointment is then created for all selected resources. This way you can for example manage team meetings easily.