- You can use these buttons to scroll the list of opened source files left and right once there are too many to fit.
- Clicking the 'X' will close the source code tab.
- Clicking the down arrow will open a dropdown list of every every open source file, similar to the picture below. 
- These are line numbers.
- This is the visit count for that line. This is actually the _highest_ visit count for the line, since (like line #44) a line can have multiple symbol points.
- This sidebar displays the location and number of uncovered symbol points in the source file. Clicking on an uncovered line will move to that location in the source code.