I cannot change the font size of package explorer in Eclipse

Question

I try to change the font size of package explorer in Eclipse from menu Window → Preferences → General → Appearance, and I fail to change

Answer 1

In Eclipse 4.7.x the CSS files are under eclipse⁩/⁨plugins⁩/⁨org.eclipse.ui.themes_1.2.1.v20170809-1435⁩/⁨css⁩/

In my case I use the dark theme for OSX, so I opened the file e4-dark_mac.css and added the font-size line:

CTabFolder Tree, CTabFolder Canvas {
    background-color: #2F2F2F;
    color: #CCC;
    font-size: 13pt; // new 
}