AssetDatabase.CreateFolder
static function CreateFolder(parentFolder: string, newFolderName: string): string;
Parameters

parentFolder The name of the parent folder.
newFolderName The name of the new folder.
Returns
string The GUID of the newly created folder.
Description

Create a new folder.

		string guid = AssetDatabase.CreateFolder("Assets", "My Folder");
		string newFolderPath = AssetDatabase.GUIDToAssetPath(guid);