Where is the "code snippet" button?

Question

The first button on the left of my toolbar is the home button, followed by the arrow button that gives me access to the drop-list with "edit story javascript," "edit story stylesheet," etc. The only other buttons are "quickfind", three different buttons that control display mode, the test button, the play button, and the new passage button.

I don't see any buttons/toolbars at all when I edit the code of a specific passage. I am using the ubuntu 16.04 OS if that helps.