While your video is generating, you can continue working on other projects. All you have to do is select the 'Run in background' button on the video generation pop-up.
Please note that it would take a few seconds for this button to be activated.
To see the progress of the video generation, please click on the bell icon on the top right.
Once the video is generated, you will see an In-App notification/pop-up as well as receive an email, if notifications are enabled as in the screenshot below
Please see, clicking on the 'x' on either of the screens will stop the video generation.