How to print Star pattern

What is your use case? Is this a test? I suggest to study the list of Appian functions here https://docs.appian.com/suite/help/22.4/Appian_Functions.html

Below some code:

a!forEach(
  items: enumerate(5),
  expression: rept("*", fv!index)
)

There are already a lot of similar threads about this topic. From next time, please try to search in the existing discussions. You might find something more useful

a!forEach(
  items: enumerate(5),
  expression: joinarray(repeat(fv!index,"*"),"")&char(10)
)