There is now (Eclipse 4.17, July 2020) an official setting:
The font used for tree and table views can now be customized with a font preference. This preference is called “Tree and Table font for views” and can be found in Window > Preferences > General > Appearance > Colors and Fonts under the “View and Editor Folders” category.
The Project Explorer is an example of a view that gets affected by this font preference.
