I'm not able to apply discounts for my products while invoicing. Even after adding discounts, it is not reflecting in my invoice.this problem persists only in Mobile app.

I have a good news for you, @Planting.

The capability to assign discounts per line item in sales forms (invoices, sales receipts, and credit notes) has now been added in QuickBooks Online. It is in addition to each transaction level discount that was already available.

You'll need to enable the line-level or item-wise discount from an invoice in the system. 

Here's a demonstration on how to do this:

To give you complete details on how to manage discounts on invoices, please refer to this link: Discount by line item on invoices and sales receipts.

I'm always up for further assistance if there's anything else that you need, @Planting. Just notify me by leaving a reply below. Keep safe!