This is a quick & dirty script for finding missing labels in DFO365 by comparing those in en-GB with those in es. A lot could be done to make this more re-usable (e.g. currently very focussed on the 2 stated languages / could easily be adapted to run for all languages / with optional filters to restrict the languages reported on); but for now it…

Search-Dfo365MissingLabels.ps1

function Convert-XmlToHash {
    [CmdletBinding(DefaultParameterSetName = 'XmlDocument')]
    Param (
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ParameterSetName = 'XmlDocument')]
        [System.Xml.XmlDocument]$XmlDocument
        ,
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ParameterSetName = 'XmlElement')]
        [System.Xml.XmlElement]$InputObject
        ,
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ParameterSetName = 'XmlText')]
        [System.Xml.XmlText]$XmlText
        ,
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ParameterSetName = 'XmlAttribute')]
        [System.Xml.XmlAttribute]$XmlAttribute
    )
    Process {
        switch ($PSCmdlet.ParameterSetName) {
            'XmlDocument' {
                $XmlDocument.DocumentElement | Convert-XmlToHash
            }
            'XmlElement' {
                [System.Xml.XmlNode[]]$children = ([System.Xml.XmlNode[]]$InputObject.Attributes) + ([System.Xml.XmlNode[]]$InputObject.ChildNodes)
                [hashtable]@{
                    "$($InputObject.LocalName)" = $children | Convert-XmlToHash
                }                
            }
            'XmlText' {
                $XmlText.Value
            }
            'XmlAttribute' {
                [hashtable]@{
                    "@$($XmlAttribute.LocalName)" = $XmlAttribute.Value
                }
            }
        }
    }
}
function Get-Dfo365LabelFileInfo {
    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true, HelpMessage = 'The path of the MetaData directory.  e.g. K:\AosService\PackagesLocalDirectory\')]
        [ValidateScript({
            if(-Not ($_ | Test-Path) ){
                throw "$_ is not a valid path" 
            }
            if(-Not ($_ | Join-Path -ChildPath 'ApplicationSuite' | Test-Path) ){
                throw "$_ is not a valid metadata path (i.e. does not contain a definition for the ApplicationSuite model)" 
            }
            return $true
        })]
        [System.IO.DirectoryInfo]$Path
    )
    Process {
        $Path | 
            Get-ChildItem -Recurse -Directory | 
            Where-Object { $_.PSIsContainer -and $_.Name.Equals('AxLabelFile')} |
            Get-ChildItem -Filter '*.xml' |
            ForEach-Object {
                $currentFilename = $_.FullName
                try {
                    [xml](Get-Content -Path $currentFilename -Raw) | 
                        Where-Object {$_.SelectSingleNode('/AxLabelFile')} | #only return valid label definitions
                        Convert-XmlToHash | ForEach-Object{[PSCustomObject]$_} | #convert from xml to ps object
                        Add-Member -MemberType NoteProperty -Name 'ThisFilePath' -Value $currentFilename -PassThru |
                        Add-Member -MemberType NoteProperty -Name 'RootPath' -Value $Path -PassThru |
                        Add-Member -MemberType ScriptProperty -Name 'LabelFilePath' -Value {(Join-Path -Path $this.RootPath -ChildPath $this.AxLabelFile.RelativeUriInModelStore)} -PassThru 
                } catch [System.Management.Automation.PSInvalidCastException] {
                    if ($_.Exception.InnerException -as [System.Xml.XmlException]) {
                        #if there's files containing XML that can't be parsed spit out an error, but don't break the flow
                        Write-Error "'$currentFilename' is not a valid XML file"
                    } else {
                        #other types of exception, push up the stack to handle (output the filename in a warning though to help investigate)
                        Write-Warning "Issue occurred processing '$currentFilename'"
                        throw 
                    } 
                }
            } 
    }
}
function Import-Dfo365LabelFile {
    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string]$LabelFilePath
    )
    Process {
        $result = [System.Collections.Generic.Dictionary[string,string]]::new() 
        Get-Content -Path $LabelFilePath | 
            Where-Object {$_ -notlike ';*'} | 
            ForEach-Object {if($_ -match '^(?<Key>[^=]*)=(?<Value>.*)$'){$result.Add($Matches['Key'], $Matches['Value'])}}
        $result
    }
}

Clear-Host
#expand the output width so stuff doesn't get truncated
$host.UI.RawUI.BufferSize = new-object System.Management.Automation.Host.Size(800,20000) 
[PSObject[]]$labelFiles = Get-Dfo365LabelFileInfo -Path 'K:\AosService\PackagesLocalDirectory' 
[PSObject[]]$en = $labelFiles | Where-Object {$_.AxLabelFile.Language -eq 'en-GB'} 
[PSObject[]]$es = $labelFiles | Where-Object {$_.AxLabelFile.Language -eq 'es'}
$labelFiles = $null

Write-Host 'Files in common' -ForegroundColor Green
$labelFileIds = $en.AxLabelFile.LabelFileId | Where-Object {$_ -in @($es.AxLabelFile.LabelFileId)} | Sort-Object -Unique
$labelFileIds

Write-Host 'Files we have for EN-GB but not ES' -ForegroundColor Green
$en.AxLabelFile.LabelFileId | Where-Object{-not ($_ -in @($labelFileIds))}

Write-Host 'Files we have for ES but not EN-GB' -ForegroundColor Green
$es.AxLabelFile.LabelFileId | Where-Object{-not ($_ -in @($labelFileIds))}

#reduce our data to the intersects, so we can compare at label file level
$en = $en | Where-Object{$_.AxLabelFile.LabelFileId -in @($labelFileIds)}
$es = $es | Where-Object{$_.AxLabelFile.LabelFileId -in @($labelFileIds)}

Write-Host 'Missing Labels' -ForegroundColor Green
$enDict = [System.Collections.Generic.Dictionary[string,[System.Collections.Generic.Dictionary[string,string]]]]::new()
$esDict = [System.Collections.Generic.Dictionary[string,[System.Collections.Generic.Dictionary[string,string]]]]::new()
$en | ForEach-Object { $enDict.Add($_.AxLabelFile.LabelFileId, ($_.LabelFilePath | Import-Dfo365LabelFile))}
$es | ForEach-Object { $esDict.Add($_.AxLabelFile.LabelFileId, ($_.LabelFilePath | Import-Dfo365LabelFile))}
$en = $null
$es = $null

$labelFileIds | ForEach-Object {
    [string]$labelFileId = $_
    [string[]]$labelIds = @($enDict[$labelFileId].Keys) + @($esDict[$labelFileId].Keys) | Sort-Object -Unique
    $labelIds | ForEach-Object {
        $labelId = $_
        [pscustomobject]@{
            LabelFileId = $labelFileId
            LabelId = $labelId
            en = if ($enDict.ContainsKey($labelFileId) -and $enDict[$labelFileId].ContainsKey($labelId)) {$enDict[$labelFileId][$labelId]} else {$null} #$enDict[$labelFileId][$labelId]
            es = if ($esDict.ContainsKey($labelFileId) -and $esDict[$labelFileId].ContainsKey($labelId)) {$esDict[$labelFileId][$labelId]} else {$null} #$esDict[$labelFileId][$labelId]
        }
    }
} | Where-Object {[String]::IsNullOrWhiteSpace( $_.en ) -or [String]::IsNullOrWhiteSpace( $_.es )} |  #Where-Object {$_.en -ne $_.es} | #use this latter where for differing labels 
    Format-Table -Property LabelFileId, LabelId ,en, es -AutoSize