You can define a variable using the equals sign. For example:

Variables Keyboard

You can add frequently used variables that will work across all your files.

To make a new variable, tap the purple +. To change the variable's name or value, hold down on it, and select edit.

Rearranging Variables

Hold down on a variable and choose "move". You then rearrange variables in the same way you arrange icons on your home screen.

Tap "Done" button when you're finished.