> As per the design view all plugin should have an access to environment variables that would be more generic.
It is not a Jenkins design. Each plugin has its own choice whether to handle env vars or not. If you see it mentioned in documentation anywhere, please provide me a link, Then it will be a bug which we would need to fix.
> And I have seen the SCM source code, the build parameters are not injected to that. Please let me know that if you can able to make a small change...
As I mentioned above, this small change needs decisions about the behavior in cases when Environment variables do not exist. And it should be a non-breaking behavior (you can see how much fun I had with it in the Perforce plugin).
You have not responded to my question about the desired behavior yet, in the current state I see no way to iterate on it.