How to redirect a query from text input to dialogflow webviewer for building app that includes a chatbot?

I am trying to build an app that takes in text input for chat app but also redirects this text input to a chatbot using dialogflow. Please see the images below. Can I redirect the text to dialogflow using post message? Or is there a way to sync the text and chatbot messages so that the user dont need to type the same query twice. Appreciate your help. Thanks!
Screenshot 2021-05-29 at 10.48.52 PM

Adding the app design for reference:

You can set a variable to a text input’s text and that way you can use the variable in as many places as you want.

But dialogflow has its own textbox that text content we have no access to. I want to send my text input to dialogflow box.

Okay, sorry, I’m not familiar with that.