Serial number column in Tabular as shown in the figure


1. Add UDDC as shown below with default value as 1.



2. After that apply data operation of Row Cumulative Sum as shown below.  Also, you can format it and remove the decimal values.


Note: This article is based on ElegantJ BI Version 4.1. This may or may not be relevant to the ElegantJ BI version you may be using.