udiMagic does NOT support deletion of unused StockItem masters. However, you can use the inbuilt functionality of Tally ERP 9 to delete unused StockItems as shown below :
- Select option "Gateway of Tally >> Display >> List of Accounts"
- Select "Stock Items"
- Select "Show Unused"
- Select "Select All"
- Press "Alt + D"
IMPORTANT
For safety purpose, it is suggested that you take backup of your Tally data before performing the aforesaid steps.