I want to hide this icon, what is icon for

[Harsh1202]

It is blocking my view to the files i have for Project. I want to hide that i marked in circle, Priviously it was not there. Now i am out of option 

 

[Meg The Dog]

Click on the stack of three lines next to the Project Name Tab at the top of the panel and from the drop down menu, toggle (uncheck) Preview Area:

MtD