Hi, it is not possible to prevent that if no zero appears in the sample. If a zero-leading number appears in the sample (other than a decimal), DSS should consider it as text automatically.
For some recipes, DSS will automatically propagate the forced "Text"
However, there is a catch with Excel export: Excel export does not currently respect the types, and will always remove the leading zeros. To work around, use CSV export instead of Excel export. Beware that when importing the resulting CSV into Excel, Excel will also remove the leading zero, unless you force "text" format in the Excel import wizard.