If we have setup multi-tenancy in SDM i.e. Tenant A and tenant B. Can we create contact affected end user/employee i.e. UserA belong to two tenant? so that if analyst tenant A can open incident for this userA in tenant A and analyst tenant B can open incident for this UserA as well in tenant B.
I'm sorry to say that I don't believe this would be possible using tenancy as it is designed. A contact record is only associated to one tenant, it wouldn't be possible to specify multiple tenants to a contact.
If you were to use a sub-tenants or tenant groups though it may be possible for an analyst in Tenant A to create a ticket for a user who belongs to Tenant B, but the tenant of the user would still be "Tenant B".