You can use an existing smallcase to start with, and customize the stocks (add or remove stocks), change weights and then buy. When you do this, you will not receive any updates made to the original version of the smallcase though – so only customize a smallcase if you know what you’re doing
You can customize a smallcase from the Stocks & Weights tab of that smallcase page
Once you're on the Customize page, you can add or remove stocks, adjust quantities and change the weights.
You can only add NSE stocks to create/customize your smallcase
Your smallcase will be private and will be visible only to you