Following works BUT it must be in a separate changeset than the createtable
<createIndex indexName="XCR_ACTIVE" tableName="Z_CS_CAPV_VEH_DELTA">
<column name="ETL_ACTIVE_FL"/>
</createIndex>
<modifySql dbms="mssql">
<append value=" WHERE ([ETL_ACTIVE_FL]='N')"/>
</modifySql>