Trigger-based template sensor: using "this" inside "trigger" not possible I guess

Consider this trigger-based template sensor:

template:
  - trigger:
      - platform: template
        value_template: >-
          ...
    sensor:
      name: xyz
      state: >-
        ...

I may use a “this” variable inside the “sensor” section.
But can I use this variable inside “value_template”?

Use-case:
some “sensor.xyz” depends on “sensor.xyz_xyz”:

  - trigger:
      - platform: template
        value_template: >-
          {% set ENTITY_ID = 'sensor.xyz_xyz' %}
          {{ ... do smth with ENTITY_ID ... }}

But I would like to declare as:

  - trigger:
      - platform: template
        value_template: >-
          {% set ENTITY_ID = this.entity_id + `_xyz' %}
          {{ ... do smth with ENTITY_ID ... }}

Have not tested yet by myself, but I doubt that “this” may work here…
Also, ONE trigger may be used by several sensors which is one more prove that “this” cannot be used here.

this is only available in the sensors themselves. the trigger occurs before the sensor(s). Just take a step back and think about this logically…

what would this be in the trigger if yoru configuration was

template:
- trigger:
  - platform: ...
    ...
  sensor:
  - name: x
    ...
  - name: y
    ...

This is valid yaml. So if this was allowed in triggers, what would this reference? x or y? Typically, you can use these types of scenarios to answers these questions.

A similar thought came to my mind earlier:

Thanks a lot for your prove!