One big customer feedback was making QBO work better when opened in multiple browser tabs. We have made some improvements in this area too. First you will notice that every navigation point (something you can click on to go a different page) is now a simple URL. Left menu items, top menu items, certain blue colored links on the page etc. Which means you can just right click any of them and open in a new tab or window. Likewise you can CTRL / CMD + click too, to open that page in a new tab. This is very much like other websites on the web and something you could not do in the old QBO.
Secondly, when working in certain areas you should see data sync between the tabs. So if you had the customer center open in one tab, and you added a new invoice in the other tab, the customer center should automatically refresh with the new data. You no longer have to manually refresh the browser in such scenarios to see updated data. Likewise adding a new customer or product in one tab, it should be available in the other tabs without a refresh.