Keyboard Maestro 8 adds a preference (in the General Preferences) to control the text size in the editor and switchers. You can select from:
The setting will affect the size of the next in the Macro Groups and Macros column, action selector, library, and the Clipboard Switcher.
So if you have a small retina screen and really good eyesight, you can set the text size smaller, and if your eyes are getting a bit old other otherwise need a bit of help, you can set the text larger.
Note that the setting doesn't affect everything, in particular the actions in the action editor are not affected. Maybe they will be one day, but for now, at least you'll know which macro you are editing!