Android (root): Text expansion is one of the most useful features of desktop operating systems. On mobile, they're a bit more rare. You can use shortcuts in the stock Android keyboard, but the Macro/Text Expansion Xposed module is for you if you want expansion everywhere.
This module allows you to put large chunks of text into small shortcuts that are accessible via any keyboard that is currently installed. The module operates at the text-widget level, which simply means that anywhere you find a regular text field, your shortcuts will work (although, presumably, not in password fields).