How to Change Android Studio's Project Panel Font Size

SOURCE

Go to:

File | Settings | Appearance & Behavior | Appearance

And then tick on:

[ ] Override default fonts by (not recommended)
    Name: Ubuntu       Size: 14

There you can choose the font and the size of everything: menus, Project panel, Editor, etc... For me, on Linux, it is fine to set it to 15 (default is 14), and then adjust the Editor font alone under:

Editor | General