Construct variable from another variables

{% load_yaml as yaml %}

test:
  dev: 'xxxxx'
test_2:
  dev: 'yyyyy'

{% endload %}

{% set proj = slspath.split('/')[0] %}
{% set env = slspath.split('/')[1] %}
{% set service = slspath.split('/')[2] %}

{% set a = yaml ~ '.' ~ proj ~ '.' ~ env %}

test:
  cmd.run:
    - name: echo {{ a }}

Output:

test:
  cmd.run:
    - name: echo {'test': {'dev': 'xxxxx'}, 'test_2': {'dev': 'yyyyy'}}.test.dev    <======================

Is it possible to access test yaml from dynamically created variable?

As I really want to return yaml.test.dev value no entire yaml + test.dev...

No source file, test, or entry point is identified. Start by reproducing the provided Salt template and inspecting how the dynamically assembled value is evaluated; done means a dynamic reference returns the nested yaml.test.dev value rather than the full mapping followed by a string path.