Allow Zigbee devices to join switch.

requirements: 

- Zigbee to MQTT Bridge (zigbee2mqtt add-on)

Add this to your configuration.yaml

# zigbee ------------------------------
# Input select for Zigbee2mqtt debug level
input_select:
  zigbee2mqtt_log_level:
    name: Zigbee2mqtt Log Level
    options:
      - debug
      - info
      - warn
      - error
    initial: info
    icon: mdi:format-list-bulleted

# Input text to input Zigbee2mqtt friendly_name for scripts
input_text:
  zigbee2mqtt_old_name:
    name: Zigbee2mqtt Old Name
  zigbee2mqtt_new_name:
    name: Zigbee2mqtt New Name
  zigbee2mqtt_remove:
    name: Zigbee2mqtt Remove

# Scripts for renaming & removing devices
script:
  zigbee2mqtt_rename:
    alias: Zigbee2mqtt Rename
    sequence:
      service: mqtt.publish
      data_template:
        topic: zigbee2mqtt/bridge/config/rename
        payload_template: >-
          {
            "old": "{{ states.input_text.zigbee2mqtt_old_name.state | string }}",
            "new": "{{ states.input_text.zigbee2mqtt_new_name.state | string }}"
          }
  zigbee2mqtt_remove:
    alias: Zigbee2mqtt Remove
    sequence:
      service: mqtt.publish
      data_template:
        topic: zigbee2mqtt/bridge/config/remove
        payload_template: "{{ states.input_text.zigbee2mqtt_remove.state | string }}"

# Timer for joining time remaining (60 sec = 1 min)
timer:
  zigbee_permit_join:
    name: Time remaining
    duration: 60

sensor:
  # Sensor for monitoring the bridge state
  - platform: mqtt
    name: Zigbee2mqtt Bridge state
    state_topic: "zigbee2mqtt/bridge/state"
    icon: mdi:router-wireless
  # Sensor for Showing the Zigbee2mqtt Version
  - platform: mqtt
    name: Zigbee2mqtt Version
    state_topic: "zigbee2mqtt/bridge/config"
    value_template: "{{ value_json.version }}"
    icon: mdi:zigbee
  # Sensor for Showing the Coordinator Version
  - platform: mqtt
    name: Coordinator Version
    state_topic: "zigbee2mqtt/bridge/config"
    value_template: "{{ value_json.coordinator }}"
    icon: mdi:chip

# Switch for enabling joining
switch:
  - platform: mqtt
    name: "Allow devices to join"
    state_topic: "zigbee2mqtt/bridge/config/permit_join"
    command_topic: "zigbee2mqtt/bridge/config/permit_join"
    payload_on: "true"
    payload_off: "false"

automation:
  # Automation for sending MQTT message on input select change
  - alias: Zigbee2mqtt Log Level
    initial_state: "on"
    trigger:
      platform: state
      entity_id: input_select.zigbee2mqtt_log_level
    action:
      - service: mqtt.publish
        data:
          payload_template: "{{ states('input_select.zigbee2mqtt_log_level') }}"
          topic: zigbee2mqtt/bridge/config/log_level
  # Automation to start timer when enable join is turned on
  - id: zigbee_join_enabled
    alias: Zigbee Join Enabled
    trigger:
      platform: state
      entity_id: switch.allow_devices_to_join
      to: "on"
    action:
      - service: timer.start
        entity_id: timer.zigbee_permit_join
# Automation to stop timer when switch turned off and turn off switch when timer finished
  - id: zigbee_join_disabled
    alias: Zigbee Join Disabled
    trigger:
      - platform: event
        event_type: timer.finished
        event_data:
          entity_id: timer.zigbee_permit_join
      - platform: state
        entity_id: switch.allow_devices_to_join
        to: "off"
    action:
      - service: timer.cancel
        data:
          entity_id: timer.zigbee_permit_join
      - service: switch.turn_off
        entity_id: switch.allow_devices_to_join
#Zigbee -------------------------------------------------------------------------

Restart Home Assistant.

When your HASS is up again open Configure UI and add new card choose: MANUAL CARD.

add this code:

entities:
  - entity: sensor.zigbee2mqtt_bridge_state
  - entity: sensor.zigbee2mqtt_version
  - type: divider
  - entity: switch.allow_devices_to_join
  - entity: timer.zigbee_permit_join
  - entity: input_select.zigbee2mqtt_log_level
  - type: divider
show_header_toggle: false
title: Zigbee
type: entities

Click safe.

When the switch is:

OFF - "permit_join":false
ON - "permit_join":true for 60 seconds