How to make a dump notification smart? (add state of a sensor to the notification)

Configuration
1

I use add-on room-assistant to track locations of our mobile phones. This works fine, so In HA I can see where each phone is located (living, kitchen, bedroom etc).

In HA I created an automation to send me a notification every time my tracked device is changing its position. In this automation I use the action “notify.mobile_app_oneplus9pro” to actually send this notification to my phone.

I now have for example below notification, which works but is rather a dump notification:

service: notify.mobile_app_oneplus9pro
data:
  message: BT tracking - living

I want to make this notification smarter by adding the actual location to it.
I now struggle how to get this added to the automation.

I was thinking of this:

service: notify.mobile_app_oneplus9pro
data:
  data: {}
  message: >-
    service: notify.mobile_app_oneplus9pro   
    data:     
      message: >- 
      Your OnePlus is detected at: 
      {% if is_state('sensor.oneplus_9_pro_room_presence', 'firstfloor') %} firstfloor
      {% elif is_state('sensor.oneplus_9_pro_room_presence','living') %} living       
      {% elif is_state('sensor.oneplus_9_pro_room_presence', 'bedroom') %} bedroom
      {% elif is_state('sensor.oneplus_9_pro_room_presence', 'kitchen') %}kitchen 
      {% elif is_state('sensor.oneplus_9_pro_room_presence','HomeServer') %} HomeServer 
      {% elif is_state('sensor.oneplus_9_pro_room_presence', 'not_home') %} not_home
      {%elif is_state('sensor.oneplus_9_pro_room_presence', 'Unavailable') %} Unavailable 
      {%endif %}

Every time I try to save the automation, a grey bar moves in my screen indicating that I have an error at “data”. So I can’t save the automation. What am I doing wrong here?

Thanks!

2 
service: notify.mobile_app_oneplus9pro
data:
  message: >- 
    Your OnePlus is detected at: {{ states('sensor.oneplus_9_pro_room_presence') }}
3

The solution above is definitely cleaner but to answer the original question…

I think if you would have indented everything below “message >-” by two spaces to the right it should have worked.