Yes you can!
Firstly you need to make sure you already have an existing project.
Secondly, create the quote and assign it to a customer and Save.
You may then find the quote in your Sales tab > Customers > Quotes > Open the quote
From here you can then assign the customer name to your Project name then select Save.
Let us know if you get stuck or still need help.
Hello @9130 3502 4965 9466,
Yes, you can link an existing quote to a project in QuickBooks Online (QBO) as long as you haven't deleted it.
In most cases, the frequently accessed page resources stored on your browser may affect your browsing experience. They can cause unexpected browser problems like how you're unable to link a quote to a project.
Let's consider logging in to your QBO account using a private or incognito window so we can isolate this issue. To do so:
On top of that, I've also included this reference for a compilation of articles you can use while working with us: Sales and Customer for QuickBooks Online.
Feel free to drop by anytime if you have any other concerns. I'll be more than happy to help you. Have a good one!