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

This worked for me using version 2019-09 on Windows 10:

• Locate the directory C:\Users\johndoe\.p2\pool\plugins in File Explorer, replacing "johndoe" with your own Windows user ID.
• Depending on what you have done in the past with Eclipse, you should see one or more directories with names that start with org.eclipse.ui.themes.
• Select the one with the most recent date modified. In my case its name was org.eclipse.ui.themes_1.2.700.v20190826-0816.
• Within that directory open the directory named css.
• Open the file named e4_default_win.css in a text editor, and append something similar to the following at the end of the file:

Tree { font-size: 24px; font: Mistral; }

• Don't pick those specific values! You should pick the font and font size you want. I deliberately made poor choices only to make the effect of those settings obvious in the screen shot below.

• Save the file and restart Eclipse. You should see that the font has been changed in the Project Explorer and Package Explorer views, and a lot of other places as well:

• Just be clear, the name of the file I edited was C:\Users\johndoe\.p2\pool\plugins\org.eclipse.ui.themes_1.2.700.v20190826-0816\css\e4_default_win.css. The name of the file you edit won't be exactly that, but it should be similar.