Once you delete a preset, there's no way to get it back, so be careful.
Dependencies
The Advanced Data Generator keeps track of dependencies: projects that use a specific preset. If you try to delete a preset that has dependencies, the following dialog will be displayed:
The Preset Dependencies dialog
Via this dialog, you can either cancel the delete action, or force a delete. The Force Delete button will delete the preset despite the dependencies in the displayed projects. However, if you re-create a preset with the same name and datatype, the preset link is re-established if you open and save the Data Generator Project.
If you try to use a project without the required preset, the project will become invalid.