Вот решение с использованием XElement:
using namespace system.xml.linq
$CurrentDate = Get-Date
$YearEnd = Get-Date -Year $CurrentDate.Year -Month 12 -Day 31 -Format yyyyMMdd
$MonthEnd = Get-Date -Year $CurrentDate.Year -Month $CurrentDate.Month -Day ([datetime]::DaysInMonth($CurrentDate.Year,$CurrentDate.Month)) -Format yyyyMMdd
$x = [xelement]::new("Trigger",
[xelement]::new("Value1",$YearEnd),
[xelement]::new("Value2",$MonthEnd),
[xelement]::new("Value3",$MonthEnd),
[xelement]::new("Value4","FINANCE"),
[xelement]::new("Value5",""),
[xelement]::new("Value6",""))
$x.tostring() | Set-Content -Path "x.xml"
Это выводит структуру XML в файл x.xml в текущем каталоге.