How to get global input and use it across all pipeline steps

Since my-input would be stored as meta-data, it would not be available in a conditional within the pipeline, but you would be able to access it in Step B. If you are wanting to use it in a conditional though, you would need to use the buildkite-agent meta-data command and some scripting. There is a great example of how to do this over in this thread:

Hope that helps!