Floating-point scalar. Translated to [code]float[/code] type in shader code.
3D vector of floating-point values. Translated to [code]vec3[/code] type in shader code.
Boolean type. Translated to [code]bool[/code] type in shader code.
Transform type. Translated to [code]mat4[/code] type in shader code.
Color type. Can be used for return icon type in members dialog (see [method VisualShaderNodeCustom._get_return_icon_type]) - do not use it in other cases!