Based on the latest FAQ, the RMCD has clarified that the GST final submission must include value of goods held to be reported in the GST-03 Return under field 5 (a). Following are the steps to report it into GST-03.
Open Stock Balance Report and select the date as of 31 August 2018 and press inquiry to get the amount.
Create Journal Entry to credit the taxable amount with SR-0 Tax Code in Sales Account (or any account). This is to pass the amount into GST-03 under field 5 (a).