Bold the text on confirmation message

Create a rule with text as rule input -

a!localVariables(
  local!lRange: 120302 - 97,
  local!uRange: 120276 - 65,
  joinarray(
    char(
      a!forEach(
        items: code(ri!text),
        expression: a!match(
          value: fv!item,
          whenTrue: and(fv!value > 96, fv!value < 123, ),
          then: fv!value + local!lRange,
          whenTrue: and(fv!value > 64, fv!value < 91, ),
          then: fv!value + local!uRange,
          default: fv!value
        )
      )
    ),
    ""
  )
)

Now call this from your interface -

{
  a!buttonArrayLayout(
    buttons: {
      a!buttonWidget(
        label: "Button",
        style: "OUTLINE",
        confirmMessage: rule!MGS_bolding(text: "hello")
      )
    },
    align: "START",
    marginBelow: "NONE"
  )
}