Passing variables to a script: default values

In blueprints there is a support of default values of input variables.
Do we have a similar support for scripts?

Here is an example:

script:
  do_something:
    fields:
      input_FLAG_1:
        selector:
          entity:
            domain: input_boolean
      input_FLAG_2:
        selector:
          entity:
            domain: input_boolean

    sequence:
      ...
      - service: script.do_something
        data:
          input_FLAG_1: input_boolean.flag_1
          input_FLAG_2: input_boolean.flag_2

I wonder is it possible to define a default value for input_FLAG_2 and not pass it every call?

You can definitely set a default… Passing variables to scripts. I’ve never tried it with a selector, but it doesn’t seem to be expressly forbidden according to the docs.

This note confuses me:
изображение

And just for test I made this:

      input_FLAG_2:
        selector:
          entity:
            domain: input_boolean
        default: binary_sensor.service_on_value  ###which is ON always

and called the script w/o input_FLAG_2:

      - service: script.do_something
        data:
          input_FLAG_1: input_boolean.flag_1

and I see this error:

Error in 'choose[0]' evaluation: In 'template' condition: UndefinedError: 'input_FLAG_2' is undefined

So it seems that default option is only for UI.

This is likely a solution for the original problem.
You can have variables in scripts & script Blueprints as well as fields, so…

fields:
  thing_1:
    ---
variables:
  thing_1: >
    (% if thing_1 | default('') %}
      thing_1
    {% else %}
      "default value"
    {% endif %}