Discounts are an awesome way for you show your customers how much you appreciate them. Creating estimates in QuickBooks Online is really simple, and I'd be happy to explain how discounts work on your sales forms.
At this time, you're only able to add one discount to the overall estimate or invoice. I know how handy it would be for you to be able to add multiple discounts on your estimate. I'd be happy to submit your feedback about this to our product development team for review. I'd encourage you to do the same by clicking the Gear icon > Feedback.
We're always looking for new ways to improve QuickBooks Online, and user suggestions are always appreciated.
If you have any other questions, please reach out to our tech support team for further assistance.