Você está procurando '\ f 'mudar :
\f
Specifies the text to be inserted following the MergeField field if the field is not blank.
e o exemplo:
{ MERGEFIELD CoutesyTitle \f " " }{ MERGEFIELD FirstName \f " " }{ MERGEFIELD LastName }
Results in the following:
If all fields are present: Ms. Mindy Martin
If FirstName is missing from the data source: Ms. Martin