The first button group in the toolbar is for Scheme-it project management.
The "Save" button will update (save) your current project. It behaves like 'Save As' button if the project is newly created or is not yours.
The "Save As" -> "A new Project" button will save current project as a new one. This feature is useful if you want to modify an existing project and save it under a new name.
The "Save As" -> "A new Revision" button will create a revision of your currently opened project.
"New" -> "Blank Project" button creates a new project. If you have an existing project open with unsaved changes, Scheme-it will prompt you to save your changes before creating a new project.
"New" -> "Design Starter" lets you browse projects from Design Starters - a collection of designs that might give you a running start for your next one.
The "Open" button lists project in Design Starters. If you are logged in, your projects will be listed there as well, in a new dialog tab. Project list is paginated, with sorting and filtering capabilities.
The "Notes" button opens an editor that manages Summary and Description of the current project.
Opening a shared or pubic project does not require you to register or log in.
If you want to save other's project or to make your own, a Digi-Key account is required. The registration is free, you can do it in either way: