Writing Expressions
Most text input fields in Flow Designer support writing expressions. Expressions are not required, but they allow for powerful scripting functionality through variables for advanced users. You can also enter basic text and numbers in the same input fields for simple flows if you do not need expressions.
Wrap each expression in double curly brackets as seen here: {{Enter Expression}}
For example, if you want to combine two string variables together, you must use {{var1+var2}}. For more information see: https://pebbletemplates.io/.