I harvest by Parafin huge directory. It's create such file  SDK.wxi
<include>
  <fragment>
    <componentgroup id="user-content-group_SDK">
      <componentref id="user-content-comp_SDK_0">
      <componentref id="user-content-comp_SDK_1">
       ....
      <componentref id="user-content-comp_SDK_751">
    </componentref></componentref></componentref></componentgroup>
    <directoryref id="user-content-INSTALLDIR">
      <directory id="user-content-dir_Intellexer_SDK_0" name="Intellexer SDK">
        <component id="user-content-comp_SDK_0" diskid="1" keypath="yes" guid="3DEDAE66-12F2-4E7A-BDE7-A16EFE1017AB">
          <file id="user-content-file_SDK_0" source="$(var.SDK.Path)\ISDK_License.xml">
        </file></component>
        <directory id="user-content-dir_Intellexer_SDK_Bin_1" name="Bin">
          <component id="user-content-comp_SDK_1" diskid="1" keypath="yes" guid="DEA33E99-9166-4139-A3D8-C8E3711CE826">
....
       </component></directory>
      </directory>
    </directoryref>
  </fragment>
</include>
Question: how can I include in main module file ComponentGroup Id="group_SDK"
main module file
<wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
  <module id="user-content-IntelexerSDK" language="1033" version="1.0.0.1">
    <package id="user-content-{GUID}" description="Intelexer SDK" manufacturer="$(var.Project.Manufacturer)" comments="Intelexer SDK." installerversion="200" compressed="yes">
    <directory id="user-content-TARGETDIR" name="SourceDir">
      <directory id="user-content-ProgramFilesFolder">
        <directory id="user-content-INSTALLDIR" name="$(var.Project.Manufacturer)">
   </directory>
            </directory>
          </directory>
        
      
    
  </package></module>
  </wix>