Well I created a quick script that I run but you can have Inventory run it but I just needed it once for all devices:
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@ECHO ON
set CWD=%~d0%~p0
cls
C:
if %PROCESSOR_ARCHITECTURE% ==AMD64 (
ECHO Preferred Server List x64
FOR /F "delims==" %%1 IN ('type "%PROGRAMFILES(X86)%\LANDesk\LDClient\sdmcache\preferredservers.dat"') DO REG ADD "HKEY_LOCAL_MACHINE\System\LANDesk" /v "Preferred Server" /t REG_SZ /d "%%1" /f
ECHO %ERRORLEVEL%
sdclient.exe /msg=Preferred64_ERRORLEVEL_is_%ERRORLEVEL%
) else (
ECHO Preferred Server List x86
FOR /F "delims==" %%1 IN ('type "%ProgramFiles%\LANDesk\LDClient\sdmcache\preferredservers.dat"') DO REG ADD "HKEY_LOCAL_MACHINE\System\LANDesk" /v "Preferred Server" /t REG_SZ /d "%%1" /f
ECHO %ERRORLEVEL%
sdclient.exe /msg=Preferred32_ERRORLEVEL_is_%ERRORLEVEL%
)
EXIT /B %ERRORLEVEL%
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Then I just created a Custom Data Registry Key to pull the info into Inventory:
Root Key - HKLM
Key - System\LANDesk
Value - Preferred Server
Attribut Name - Custom Data - LANDesk - Preferred Server