On this page, I have listed some tools and services that I recommend for Dialogflow bot makers.
Airtable's slogan is "works like a spreadsheet but gives you the power of a database". That is a good summary of the service. It is what I currently recommend that you use as the backend for your Dialogflow prototype bot. It has some features which make it particularly well suited for creating Dialogflow chatbots.
Before I found Airtable, restdb.io was the tool I recommended as a low-code database option for Dialogflow bot makers. I even used it to created my free "Step-by-step guide to Dialogflow for non-programmers" YouTube course. However, at this point I recommend Airtable if you are going to build Dialogflow chatbots.
XMind is an excellent mind-mapping tool and is one of the best tools for creating Dialogflow flowcharts. Unfortunately, it is a desktop app. Plus some time back they also removed the DropBox like cloud sharing option. This means it is a little more limited when it comes to collaboration.
Mindomo is a web based mind-mapping tool and an alternative to XMind, and also an excellent tool for creating Dialogflow flowcharts. You get all the features which you need for creating solid Dialogflow flowcharts, plus the usual benefits of a web based tool such as easier sharing and collaboration.
Postman is a very handy tool when you wish to create an integration which uses Dialogflow's REST API, and just to understand how different APIs (and not just Dialogflow) work in general. In fact, I explain how non-programmers can use Postman to explore and understand Dialogflow's REST API in my online course.