Output of qwinsta.exe varies depending on OS language. Column length seems to vary between OS versions. This is a try to reliably convert the text output of qwinsta.exe.

getQwinstaSessions.ps1

# Get text output of qwinsta
$qwinstaOutput = &qwinsta.exe

# Column definitions (in the order as they appear in the output of qwinsta)
#   Name         --> Name of the property in the output object
#   Start        --> Should always be 0 and is detected automatically later in the script (varies depending on the output language)
#   Length -eq 0 --> Column is left aligned with variable length (detected later in the script)
#   Length -gt 0 --> Column is right aligned with fixed length
$columnInfo = @(
    [PSCustomObject]@{
        Name   = 'SessionName'
        Start  = 0
        Length = 0
    },
    [PSCustomObject]@{
        Name   = 'UserName'
        Start  = 0
        Length = 0
    },
    [PSCustomObject]@{
        Name   = 'ID'
        Start  = 0
        Length = 5
    },
    [PSCustomObject]@{
        Name   = 'State'
        Start  = 0
        Length = 0
    },
    [PSCustomObject]@{
        Name   = 'Type'
        Start  = 0
        Length = 0
    },
    [PSCustomObject]@{
        Name   = 'ComputerName'
        Start  = 0
        Length = 0
    }
)

# Detect position of first character of each column ($columnInfo.Start) and the length of the column ($columnInfo.Length) by analysing the header row
$currentCharNumber = 0 # current character position
$currentColNumber = 0 # current table column (i.e. array index of $columnInfo)
$isLastCharWhitespace = $true # helper to detect if new column starts
$headerCharArray = [char[]]$qwinstaOutput[0] # convert header row to char array
foreach ($character in $headerCharArray) {

    # cannot be a new line if its a whitespace or the "current session indicator" (>) in the first char column
    if ($character -ne ' ' -and ($character -ne '>' -or $currentCharNumber -gt 0)) {

        # if last char is non-whitespace, it's still the same column
        if ($isLastCharWhitespace) {        

            # left aligned column with variable length
            if ($columnInfo[$currentColNumber].Length -eq 0) {
                $columnInfo[$currentColNumber].Start = $currentCharNumber
            }

            # right aligned column with fixed length
            else {
                $columnInfo[$currentColNumber].Start = $currentCharNumber - $columnInfo[$currentColNumber].Length
            }

            # set length of previous column if we are currently not in the first column
            if ($currentColNumber -gt 0) {
                $columnInfo[$currentColNumber - 1].Length = $columnInfo[$currentColNumber].Start - $columnInfo[$currentColNumber - 1].Start
            }
            $currentColNumber++
        }
        $isLastCharWhitespace = $false
    }
    else {
        $isLastCharWhitespace = $true
    }
    $currentCharNumber++
}

# set the length of the last column
$columnInfo[-1].Length = $headerCharArray.Length - $columnInfo[-1].Start

# create output object
$sessions = [System.Collections.Generic.List[PSCustomObject]]::new()

# process each row except the header row
foreach ($line in ($qwinstaOutput | Select-Object -Skip 1)) {
    $session = [ordered]@{}

    # process each column
    foreach ($column in $columnInfo) {
        $session[$column.Name] = $line.Substring($column.Start, $column.Length).Trim()
    }

    $sessions.Add([PSCustomObject]$session)
}

$sessions