Start lex intent without utterance

You can use Lambda to call Lex's API RecognizeText to give it hints and so it starts on a particular intent, get the next message and play that as the prompt in Get Customer Input block.

But if this is the beginning of the bot and it is just at the welcome message, how would you know which intent to lead the bot? Normally you would have come from somewhere like caller dialed a specific phone number that matches an intent so you can do the above. Or play a generic message if they dialed a main number, etc.

If this is webchat, you can use Step by Step guide to put a "menu" up using Cards, invoke RecognizeText with that intent, then continue with GetCustomerInput block with Lex to transition back to a regular chat with Lex afterwards.