You can make site-wide changes to settings in the site (eg fonts, colours, sizing) using the Find & Replace feature.
To enable this, go into the area you wish to change (eg Title Font). Right click in the title font field and it opens a menu > click Find and Replace.
This opens up a new window, where you can select what you want changed (this will be prefilled based on what you clicked on), where you want it changed (that page only, site-wide etc), and what you want it changed with.
Very useful if you’ve spotted a few places where the wrong font has been used, or header sizes are inconsistent.