Duplicate in key (Muenchian Grouping)

Question

it may sound strange, but is it the case that, for example, if we group it based on 3 things and also want to see a recurrence of a certain element in the key? Can anyone give a simple example if this exists? Although I searched for previous solutions, I only found one where duplicates were deleted.

I finally have my example.

My XML:

<?xml version="1.0" encoding="UTF-8"?>
<invoices>
    <invoice buyer="Company_1">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="1878.95"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_1">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="0.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_1">
        <invoicenumbers>
            <invoicenumber name="5678"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="1900.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_1">
        <invoicenumbers>
            <invoicenumber name="5678"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="0.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_2">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="1900.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_2">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_2"/>
        </cost>
        <amounts>
            <amount localamount="2700.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_2">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_3"/>
        </cost>
        <amounts>
            <amount localamount="500.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_3">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_1"/>
        </cost>
        <amounts>
            <amount localamount="0.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_3">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_2"/>
        </cost>
        <amounts>
            <amount localamount="100.00"/>
        </amounts>
    </invoice>
    <invoice buyer="Company_3">
        <invoicenumbers>
            <invoicenumber name="1234"/>
        </invoicenumbers>
        <cost>
            <COSTGROUP name="Group_3"/>
        </cost>
        <amounts>
            <amount localamount="5000.00"/>
        </amounts>
    </invoice>
</invoices>

My XSLT:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="urn:schemas-microsoft-com:office:spreadsheet" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet" xmlns:html="http://www.w3.org/TR/REC-html40">
    <xsl:output method="xml" encoding="UTF-8" indent="yes"/>

    <xsl:key name="Muenchian_Grouping" 
        match="/invoices/invoice"
        use="concat(@buyer, '|', invoicenumbers/invoicenumber/@name)"/>
    
    <xsl:key name="Muenchian_Grouping_by_costgroup" 
        match="/invoices/invoice"
        use="concat(@buyer, '|', invoicenumbers/invoicenumber/@name, '|', cost/COSTGROUP/@name)"/>  

    <xsl:template match="/">
        <Workbook>
            <Worksheet ss:Name="Report">
                <xsl:call-template name="ws_table"/>
            </Worksheet>
        </Workbook>
    </xsl:template>


    <xsl:template name="ws_table">
        <Table>
            <xsl:call-template name="columns"/>
            <xsl:call-template name="columnHeader"/>
            
            <xsl:apply-templates select="invoices/invoice[generate-id() = generate-id(key('Muenchian_Grouping', 
                concat(@buyer, '|', invoicenumbers/invoicenumber/@name))[1])]" mode="invoices"/>
        </Table>
    </xsl:template>

    <xsl:template name="columns">
        <Column ss:Width="269.25"/>
        <Column ss:Width="218.25"/>
        <Column ss:Width="291.75"/>
        <Column ss:Width="276.75"/>
        <Column ss:Width="276.75"/>
    </xsl:template>

    <xsl:template name="columnHeader">
        <Row>
            <!-- buyer -->
            <Cell>
                <Data ss:Type="String">buyer</Data>
            </Cell> 
            <!-- invoicenumber -->
            <Cell>
                <Data ss:Type="String">invoicenumber</Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">Group1_localamount</Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">Group2_localamount</Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">Group3_localamount</Data>
            </Cell>
        </Row>
    </xsl:template>

    <xsl:template match="invoice" mode="invoices">
        
        <xsl:variable name="Group1_data" select="key('Muenchian_Grouping_by_costgroup', 
            concat(@buyer, '|', invoicenumbers/invoicenumber/@name, '|', 'Group_1'))"/>
        
        <xsl:variable name="Group2_data" select="key('Muenchian_Grouping_by_costgroup', 
            concat(@buyer, '|', invoicenumbers/invoicenumber/@name, '|', 'Group_2'))"/>
        
        <xsl:variable name="Group3_data" select="key('Muenchian_Grouping_by_costgroup', 
            concat(@buyer, '|', invoicenumbers/invoicenumber/@name, '|', 'Group_3'))"/>
        
        <Row>
            <!-- buyer - when group1 is not exists -->
            <Cell>
                <Data ss:Type="String">
                    <xsl:value-of select="$Group1_data/@buyer | $Group2_data/@buyer | $Group3_data/@buyer"/>
                </Data>
            </Cell>
            <!-- invoicenumber - when group1 is not exists -->
            <Cell>
                <Data ss:Type="String">
                    <xsl:value-of select="$Group1_data/invoicenumbers/invoicenumber/@name | $Group2_data/invoicenumbers/invoicenumber/@name | $Group3_data/invoicenumbers/invoicenumber/@name"/>
                </Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">
                    <xsl:value-of select="$Group1_data/amounts/amount/@localamount"/>
                </Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">
                    <xsl:value-of select="$Group2_data/amounts/amount/@localamount"/>
                </Data>
            </Cell>
            <!-- Group1_localamount -->
            <Cell>
                <Data ss:Type="String">
                    <xsl:value-of select="$Group3_data/amounts/amount/@localamount"/>
                </Data>
            </Cell>
            
        </Row>
    </xsl:template>
</xsl:stylesheet>

So as you can see in the XML the "Company_1" has a duplicate value at "invoicenumber name="1234"" and at "invoicenumber name="5678"", and the question is how can i see both in the output excel file?

EDIT: Expected result: enter image description here