Hello @CyberianWolf ,
The editor and console font can be changed in Preferences (explore the menus to find this):
I am not aware of any way to change the font in the Processing IDE (also called PDE - Processing Development Environment):
Enhancements can be submitted here:
GitHub - processing/processing4: Source code for the Processing Core and Development Environment (PDE)
Read the section on Contributing to Processing
Peruse the issues tab for examples before proceeding.
Sometimes there is already a related issue open.
:)