This is not possible without meddling in the source code currently, however there is a feature request filed for this.
If you feel like you want to hack at the code, check out this part of df-core and follow the trail to related items. https://github.com/dreamfactorysoftware/df-core/blob/c5057d04fc982fce7ce00b4be2c33b17a0fb7a91/src/Components/Registrar.php