In the current responsibility center functionality, a user can be tagged to one RC only, however we have been receiving requests to have a user tagged to multiple RC's and to be able to restrict the users to transact and report only in RC's they are tagged to.
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Ideas Administrator

Thank you for your feedback. Currently this is not in our roadmap; however, we are tracking it and if we get more feedback and votes, we may consider it in the future. Sincerely, Ivan Koletic PM, Microsoft