Using: Aspose.Word JAVA 20.9
Issue similar to How to get or set Cell Vertical Alignment with TableStyle using Java but with Table Cell Margins.
TableStyle object always contains 0.0 values for bottomPadding / topPadding / leftPadding / rightPadding values.
Attaching compressed file which contains: DOCX file with custom created table style
Custom table style 1. It contains property for default cell margins - 0.1 each.
Also attaching code snippet for checking if table style margins are correctly applied.