This column is only available for fields of User or Workspace. This column is not available for any artifact.
Only subscription administrators can edit fields including custom fields for Users or Workspaces. This can be done from the setup area (hammer icon left of avatar) -> Subscription -> Fields section, see herein:
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The sub-admin can click on that column for the row of the field of his choice and select yes/no to make it visible to admins only. What is means is that the selected field will be seen by admins but not other users. This is meant as a security measure for mainly user or workspace fields which are not supposed to be exposed to everyone.
This ability is unavailable for artifact fields, which is why workspace admins or project admins will not see this column when editing or creating fields within their workspaces or projects.