TextExpander supports Dynamic Type, an iOS feature which allows you to control the visual size of text across all supporting apps on your device at once.
This means the default font size of the text in the snippet editor is the same as what you see in other Apple apps on your device.
Adjust this font size:
- Opening the Settings app on your device and choose General > Text Size.
- You will see a slider you can use to make the text in all those apps bigger or smaller.
If you want to change the look of snippet text once it is expanded, or or change its formatted in some other way, you can find out more about formatting snippet text here.