We have the parameter "MaxConcurrentUserSessions"  used to limit maximum number of concurrent sessions per user.

Please add this parameter to Control-M/Enterprise Manager - System Parameters:

1. From Configuration Manager --> Select a EM Component and go to --> System parameters --> Advanced
2. Search in the "Type" column for "GSR" --> Select any parameter and click on "+" button.
3. Add it with "MaxConcurrentUserSessions" as the name and "GUI Server" in the "Type" field:


IMPORTANT NOTES:
  - The GUI Server component needs to be recycled from the Control-M Configuration Manager to take effect.
  - This parameter needs to be defined for each individual GUI Server (GSR) that it applies to
  - This parameter cannot be applied to a specific user, this setting will apply to all users under that GUI server.

Example: Limiting the login to 1:


Note: If you have a Control-M Enterprise Manager for Distributed environment and want to limit it, you need to create at the Enterprise Manager system parameters for the main Enterprise Manager the above  "MaxConcurrentUserSessions" parameter and then a new one with "Gui Server" at the "Type" field, "*" at the "Name" and at the "Host" field write the specific hostname for the Distributed Enterprise Manager. After this you need to recycle all the GUI Servers components.