For more information about the Custom mental ray text, see Custom mental ray text.
Click the button in the Custom Text Editor to create a custom text node and assign it to the selected node in the scene. The Attribute Editor is updated.
The option menu lists all the available text nodes that were previously created. By selecting a new entry in this option menu the text assignment of the current scene entity is replaced with this newly chosen text node. Saving the scene to a Maya file also stores all the existing text nodes, both connected and unconnected. Custom text nodes have to be deleted by standard Maya methods, as the Custom Text Editor doesn't provide a way to do it.
For more information on the different types of text assignments refer to Types of text assignments.