Currently, there is no mechanism to restrict/stop concurrent CA SDM logins for the same userid.
CA SDM is intentionally designed to operate with multiple sessions to enable a variety of capabilities - for example, being able to have more than one ticket open at the same time.
Using the native tools available in a browser, such as the browser "duplicate" function, in an attempt to avoid multiple logins will result in multiple browsers being tied to the same SDM session, resulting in potential data loss due to inconsistent session handling. We do not recommend using this approach to work around existing product design and functionality