I would like to create Quarterly report (areachart) for 12 quarters from now.

This requires the plugin "Date and Time Utilities".

a!localVariables(
  local!start: todatetime(date(2020, 10, 1)),
  local!end: todatetime(date(2023, 9, 8)),
  local!quarters: a!forEach(
    items: enumerate(elapsedmonths(local!start, local!end)),
    expression: if(
      ceiling(month(edate(local!start, fv!item)) / 3) = month(edate(local!start, fv!item)) / 3,
      ceiling(month(edate(local!start, fv!item)) / 3),
      null
    )
  ),
  a!forEach(
    items: reject(isnull(_), local!quarters),
    expression: concat(
      "Qtr",
      fv!item,
      if(
        fv!item = 1,
        " " & year(edate(local!start, fv!index * 3)),
        ""
      )
    )
  )
)