What Control-b is supposed to do on the background?

According to the manual :
For get an idea of these capabilities, the user is invited to click in the background of
Dr.Geo – outside any window – and to press the key combination control-b. Choose
Tools>System Browser from the menu. The system browser that appears lets the user
explore and modify Dr.Geo source code while it is running.

But control-b wont work on my version: 19.09b , in Ubuntu 18.04
Although the text is not so clear what control-b should do ..