We revamped the menu to create a new project. Our goal is to make it easier to select the right tool to create the prototype you need. This new menu gives you access to:
Designer: to create a new Salesforce prototype
LWC Builder: to prototype Lightning Web Components and deploy them to your Salesforce
Theme Builder: to define a set of common CSS properties and tokens for your UI components that will be applied by default on your lightning web components.