Set Deployment from Variable - Custom Pipeline

[jmclean]

Hello Atlassian Support,

I do not believe there is a way to do this, however I would to outline the below ask

```
As a: bitbucket pipeline user

I would like: the ability to switch the `deployment` value based on a variable value for a Custom pipeline

In order to: simplify the lines of yaml definition and dynamically drive deployments
```

Example: The below image shows that in order to deploy to development and QA environments, I would need to copy and paste yaml bc the `deployment` value cannot be dynamically injected. Also below displays the feature request, visually