By default the Sylinkdrop.exe is found in the Symantec Endpoint Protection [SEP] client install directory
C:\Program Files (x86)\Symantec\Symantec Endpoint Protection\14.x.x.\Bin\Sylinkdrop.exe
or
C:\Program Files\Symantec\Symantec Endpoint Protection\14.x.x\Bin\Sylinkdrop.exe
With SEP 14.3 RU5 and above build Sylinkdrop.exe is missing from the install directory.
SEP 14.3 RU5 and above versions for Windows operating system.
From SEP 14.3 RU5 and above versions, Sylinkdrop.exe is not included in the install directory.
Use the below command to update new sylink.xml
smc -importsylink <sylinkpath>
Sylinkdrop.exe is available in the Tools folder in the full installer file downloaded from the Broadcom user portal and in <SEPM_dir>\Tools folder.