The Esri® Web AppBuilder for ArcGIS (WAB) is an extremely helpful application that allows you to build 2D and 3D web apps without writing code. However, in some cases you might want a little more functionality than WAB can provide right out of the box. This is when you will need to customize WAB.
Three main WAB customization options:
Adding an already developed widget – custom widgets are available for download on GeoNet, developed by the Esri Community
Extending an existing widget
Developing a custom widget.
In all three options, your WAB application with the custom widget will need to be hosted on a web server. If you are using Portal, you can host your widget and/or application on the same server Portal is installed on or it can reside on a separate web server. For instructions on adding an already developed widget (i.e. downloaded from GeoNet) in Portal 10.5.1 or later, check out this Esri blog article by Law.
Web AppBuilder for ArcGIS Developer Edition
You will need the WAB for ArcGIS Developer Edition to implement all three options except if you are using Portal. For Portal, you only need the Developer Edition if your widget requires application development. Therefore, Options 2 and 3 would require the Developer Edition for Portal.
Suggested Application Development Skills
Below are links to helpful development skills for customization scenarios two and three.
WAB Developer Edition API (Preferred)
GeoDecisions has experience with customization of WAB for clients using all three options. Please contact me if you would like to see a demonstration or discuss WAB customization further.
By Kelly Fisher, GIS Manager