Thank you for reaching out to Okta Support! From a high-end perspective, this can be achieved by syncing attributes and users from Domain A through Okta to Domain B and the other way around. However, the integration steps are a bit to complex to be detailed through a Community Question, considering the particularities and complexity of each environment. We recommend opening a support ticket, so that a tailored solution can be provided.
Kind regards, Cristian Mondiru Technical Support Engineer Okta Global Customer Care