Hi
When asking questions and working with GBC you will need to pay attention and specify the version you are using.
From the screenshot it looks like a 3.2x FGL version using a 1.00.XX GBC version.
If you look at the How Do I section of the 1.00 GBC documentation
https://4js.com/online_documentation/fjs-gbc-1.00-manual-html/howdoi/index.html you will see two entries "Display or hide the sidebar", "Customize the Chrome Bar", so you will need to figure out how to do GBC customisation.
In the 4.x FGL and GBC, hiding the sidebar or hiding the Application List as it is now known can be done with a .4st presentation style
Reuben