docs/expressions/variables.html
Variables are containers for storing data values.
The general rules for constructing names for variables (unique identifiers) are:
_).All variables must be identified with unique names.
These unique names are called identifiers. Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
Note: It is recommended to use descriptive names in order to create understandable and maintainable code
$hello_world = 'Hello World!'
$test_add1 = 5 + 6
item(title = hello_world cmd = msg(hello_world))
menu(title = test_add1)
{
$test_sub1 = 11 - 5
item(title = test_sub1)
}