“Show debug info” is a command from your command palette. You can make that appear via keyboard shortcut or (based on your picture above) by clicking the button right below the “graph view” button towards the top of the far left side of your screen. Edit: I don’t know how to describe the symbol except as “right below the graph view button in your picture above” but the symbol may have moved position if you installed or removed plugins, as @rigmarole points out below.
In case it helps, here is a post about how to set your default fonts from someone else who didn’t like how the fonts changed recently. The settings pictured in that thread are in “Settings => Appearance”.