You can add dynamic custom attributes to your node. Some applications include:
Add custom dynamic attributes by selecting Modify > Add Attribute. The Add Attribute window appears. See Add Attribute Options for more information.
When you add a custom attribute to an object, it appears in the Extra Attributes section of the Attribute Editor (and in the Channel Box, if you make the attribute keyable).
With this feature, custom attributes are dynamically added to an object. Dynamic attributes allow you to add or delete attributes on a particular node. They are different from static attributes in that they are only married to a specific instance of a node type. Although custom attributes added using this feature are dynamic attributes, they are referred to as custom to distinguish them from the built-in dynamic attributes.
For more information about different types of attributes, see Static, dynamic, and extension attributes.
Custom attributes have no direct effect on any characteristic of an object in Maya.