Hi @m.sadikot,
Thanks for the update.
If you are using Universal Login, you should have SSO. (Reference: Single Sign-On).
If this is not the case, could you clarify if you are using embedded authentication?
I found a relevant FAQ answering your question: Cannot maintain multiple user sessions in same browser
It seems that one workaround is to use a custom domain with your canonical domain so you can maintain two different sessions at the same time.
Please let me know if you have any questions.
Thanks,
Rueben