what to do with the workspace?
I did all the required coding, and it all works fine. Now what, should I be submitting it somewhere in order to get feedback or just close the window and move on?
If you want feedback you can make a post here and ask for it, but no it is not something you are required to do. The workspaces are there to enable you to easily code along with the video, once you have completed a section it is perfectly fine to just close it.
Once you move on to a different section or video that has a different workspace associated with it you will be prompted to open the new workspace, at which point you will be presented with a workspace that is setup for that section or video.