At launch, there isn't currently a way to save your video without exporting it. Using brands that you can edit and save means that any video should take less than a few minutes to fully edit and be ready to use.
When you are happy with how your video looks, simply click the Export Video button on the top left of the customisation panel. This will then take you to the My Videos page where you can see all your videos as well as the details of what was used.
If you ever need to re-create a similar video you can check what was used on this page and easily re-create it using the same ingredients. We will be looking at implementing ways for you to edit your exported videos in the near future.