Requirement :
Provide option to create a CI Validation Job only with "Validate pull requests targeting the source branch" and keep "Run Job" dropdown as optional .

As Of Now :
When we raise a PR, it initiates feature branch validation ( cos, we enabled "Validate pull requests targeting the source branch" ), and after that when we merge feature-branch to target branch, it re-initiates another validation job.
For us, it's like similar validation is running twice on different events from which we can't opt out.

Pros :

We can handle when to validate a feature branch, instead of bundling it with the CI validation Job ( Time based or source branch action based ).

It will help us to validate and fix feature branch before merging it on the target branch.