There are some tricks to knowing on which system are you logged changing the GUI color based on a system (also in Eclipse).
This will let you know if you have opened a production environment, for example.
But another problem is when we have some systems opened in different windows, we need to change to a specific system.
There is an option in SAP GUI preferences to display the system ID and client in the window title:
To enable this feature, you need to go to SAP GUI options and enable “Show system name in taskbar button” under “Interaction Design” -> “Visualization 2”