This feature request has now moved to “working on it”. The team is actively working on this request and I will share more details as they become available.
604 votesLiam commented
I have made a Website tab for WeTransfer so we can upload files using their service within Teams. However, the way tabs currently work is they have the same effect as closing a window when switching to another tab. Your last position is not remembered and the tab does not run in the background. So in order to upload a file to WeTransfer using the Website tab for example, you need to leave the tab open while the upload is in progress. This removes the possibility of multitasking within Teams.
Perhaps apply some sort of option when setting up a Website tab that says 'run this tab in the background'?