@holyone2 The custom commands GUI or speech studio allows you to export the application but you cannot add new utterances or intents from this GUI.
However, I have tried a workaround to login to luis.ai with the resource mapped to your custom commands application and the list of luis applications should display the app that was published from custom commands GUI.
In here, you can edit your intents or entities and then publish them. This ensures your custom commands application or GUI that is linked to this LUIS resource utilize the changed model or luis app and respond accordingly. For example:
If I added a random utterance in my cancel intent from luis.ai the custom commands application should be able to recognize this with a high score.
Utterance added from luis.ai:
Custom commands GUI:
Similarly I think your custom entities should also work. I found it is easier to test first from the luis.ai test screen and publish the app and then check the same scenario from your custom commands application. I hope this helps.