Замените разрывы строк пробелами перед использованием $ Description.
$web = get-spweb $siteUrl
$ caseLib = $ web.lists |где {$ _. title -eq $ listTitle}
$ query = new-object Microsoft.SharePoint.SPQuery
$ query.ViewFields = ""
$ query.RowLimit = 500000
Запись-вывод "Заголовок} Описание" |Out-File "temp.csv"
do
{
$caseLibItems=$caseLib.GetItems($query)
$query.ListItemCollectionPosition=$caseLibItems.ListItemCollectionPosition
$listItemsTotal = $caseLibItems.Count
$x = 0
for($x=0;$x -lt $listItemsTotal; $x++)
{
$Description = $caseLibItems[$x]["DocumentSetDescription"]
$str = ""
if('$Description' -ne $null)
{
$Description = $Description -replace "`n"," " -replace "`r"," "
$str = $caseLibItems[$x]["LinkFilename"].ToString() + '}' + $Description
}
else
{
$str = $caseLibItems[$x]["LinkFilename"].ToString()
}
Write-Output $str | Out-File -Append "temp.csv"
}
} while ($ query.ListItemCollectionPosition -ne $ null)
import-csv temp.csv -delimiter "}" |export-csv -NoTypeInformation -Path "result.csv"
Write-Host "Exiting"
Ответ, предоставленный Пьеро.