This YouTube video tutorial by GISman Lee presents an easy way to implement the communication among multiple customized widgets in ArcGIS Experience Builder.
With this method, you don't have to follow the complex ways of doing so as written in the Esri ArcGIS Experience Builder official website.
The method here is to combine the in-built Redux of ArcGIS Experience Builder with the ReactJS Life Cycle Functions, to establish a "pulling" style of message transactions.
https://www.youtube.com/watch?v=gQAqoasLkgY