The command to set one or more custom variables in the deck (without asking the user) is setvar
The parameters are;
Each variable name should be lowercase, begin with a letter and contain letters, numbers and the underscore character.
As with user input, values are stored with the deck (and backups). Variables can be used when programming deck buttons by prefixing the name with '$'. The example below sets the countdown variable, then uses $countdown to initialise a timer;