Is there a way of setting a global property/environment variable in one declarative pipeline and be able to use that in other pipelines?
So in pipeline A, I set a different value each time I run it. In pipeline B and C I need to read that value and use it for my run.
Not really directly. It would get messy pretty quickly if one job could affect a global state. It would really be hard to trace and everything else.
But you can use a combination of build parameters, and providing them via the build pipeline step, to trigger a new job with a bunch of variables set.