OK, I figured it out. Although this is acceptable, in isolation:
binary_sensor:
- name: 'Both Home'
unique_id: both_home
sensor:
- name: 'House Power Demand'
unique_id: house_power_demand
icon: mdi:transmission-tower
I needed to reformat to:
- binary_sensor:
- name: 'Both Home'
unique_id: both_home
- sensor:
- name: 'House Power Demand'
unique_id: house_power_demand
icon: mdi:transmission-tower
to allow adding:
- trigger:
- platform: mqtt
topic: "birdnet"
- platform: time
at: "00:00:00"
id: reset
sensor:
...