When working with a type, it is important that you configure all of the relevant properties. Otherwise, the type will be invalid, or it will not behave as expected when used in Design Studio.
All types must have a valid name. The type names must start with a letter or an underscore and must contain only letters, digits and underscores. Two types in the same project must not have the same name. The name of a type is simply its file name without the extension. E.g. a type with the file name 'ExampleType.type' will be available in Design Studio as 'ExampleType'.
Also, all types must have a type kind which indicates how the type will be used. You can choose the type kind using the "Type kind" drop-down box below the Attribute Table. Normally, it will not be necessary to select anything here, as the type kind "Standard Type" should always be used unless one has need for the legacy type kind "Database Output Type". See the reference documentation on Design Studio for more information.