I was just thinking about this feature and glad to see it logged. I completely agree with this. I used MD to support an in-class project this semester (with the free tier) and as I look ahead to future classes, it would be great if I could organize the web console.

Currently, the left hand nav on the web console has two entries: Notebooks and Attached Databases. Both expand to show child data. My comment extends above to suggest the idea of a parent folder. By default, there could be a single folder two children, Notebooks and Attached Databases. The plus button for Notebooks can be used to add a new project/folder, and then follow the same UI/X that exists today. The only difference is that the folder is an organizing unit of the same objects presented to users of the web console. This does imply a 1:1 relationship between a notebook and the folder. A folder/project can have many notebooks and attached databases, but a database can not be in two folders/projects.

To keep parity, it would be great if there was a way to remove the parent and see the list of databases as we can today.