Funnel Bookings does not currently have dedicated functionality to support multiple interviewers, this is something we are looking at improving in the future.
For now, if your multiple interviewers are running interviews at the same time the system will allow you to create multiple availabilities in the same time slot. Select the relevant Booking and select the day from the calendar view. In the edit time slot panel select the duplicate button, this will add more time slots to your calendar and you can see this indicated on the calendar by split space and the plus number icon.
If the multiple interviewers are running sessions on different days, it will be best to create these as seperate booking types per interviewer.