DataEditor Library
The (custom) DataEditor actions are stored within a separate table, which is accessed using the DataEditors action.
Create DataEditor
When you want to create a new DataEditor action, the best option is to use the "Generate DataEditor" wizard instead of creating one from scratch using the Add option.
Using this wizard, just select the table for which you want to create a DataEditor and follow the subsequent steps to generate the metatype xml, the dataeditor xml and the library configuration xml.
The wizard will also create the necessary localization strings for you and add an user action.
Edit DataEditor
Once a DataEditor action has been created, you can start testing and fine-tuning the action. Select the DataEditor from the list and click edit to make the required adjustments.