Release : 2018
Component : AGILE CENTRAL
Yes, it's possible. You can create a field on the workspace level, then make it hidden for any project you'd like, so you can hide it for all projects. While this field won't appear on the screens, it's still going to be available for the API so you can use the API to set/get information on that field. You can't hide it on the object level, but on a project by project basis. That means you can't add this field to a user story and then hide it per the user story object, you'll need to hide from specific projects so you can pick and choose where to hide and where not to hide, but as said, you can hide from all projects.