Yes, a user can add quantities to existing holdings by 

Step 1: Navigating to ‘Portfolio’ → ‘Holdings’ page.

Step 2: Select the stock for which you want to add quantity, then tap on the ‘Buy’ button. 

Step 3: Select the desired Exchange.

Step 4: An order details page will be displayed, with all details. The user needs to enter the desired quantity and price and click on the 'Review buy order' button.

Step 5: Review the details displayed on the ‘Delivery order summary’ page and Tap on ‘Submit Order' button.

Step 6: If you are not satisfied and want to change the input values, just swipe down on the ‘Delivery order summary’ page.

Step 7: You will be redirected to the Order Entry page. Edit the details you wish to change and click on the 'Review buy order' button.

Step 8: Review the details displayed on the ‘Delivery order summary’ page and Tap on ‘Submit Order' button.

Step 9: Once submitted, order requests will be placed and redirected to the Orders page.

Step 10: Once an order is traded, the trade will be displayed under the ‘Positions’ tab.