Importing a customised layout is unavailable, @max456. You'll want to make use of the built-in editor instead to personalise your sales forms. 

I can see that being able to import your own template for quotes and estimates is a great option. As of June 29, 2021, this is no longer supported for all-new QuickBooks Online accounts. This is why you only have QuickBooks Themes inside of QuickBooks Labs.

You'll want to make use of our templates and edit them according to your needs. You can check out the detailed steps here: Customise invoices, quotes, and sales receipts in QuickBooks Online

You can also view, create, and edit sales transactions from within the page. This allows you to see the status and amounts of your sales transactions at a glance. This includes open or recently paid invoices and unbilled items like quotes.

If you have follow-up questions or concerns with quotes and invoices, please don't hesitate to reply. I'll be around for you. Take care and have a lovely weekend.