What's new in version 2.12

ArcGIS Web AppBuilder (Developer Edition) 2.12 update includes support for accessibility, a new widget, and improvements to several widgets.

General

Starting with this release, support for accessibility is added to 21 widgets and five themes—each tested with selected screen readers. With incremental releases, more widgets and themes will support accessibility.
You can control which layers are visible through the URL parameter, showLayers.
Transport Layer Security (TLS) version 1.0 and 1.1 are disabled by default in Node server. See Esri TLS support for details.

The new Network Trace widget utilizes a geoprocessing service to trace a geometric network and interact with its results. For example, a user specifies the location of the main break to generate the outage area.
Scalebar has a new option to display the scale number.
You can display the custom basemap in Overview Map.
You can control which layers are visible with a new link option in Share.
From the parent (group) layer, you can enable the pop-ups or open the attribute tables for all sublayers in Layer List.
Query adds an option to let you control if end users can provide a different name for the result layer name at runtime.
Swipe provides an option to hide the layer choosing list.
Smart Editor has made it easier to streamline workflows by adding Smart Action and Attribute Action options.
When using Cost Analysis, it's easier to generate a centroid of the project area by updating multiple configurations within the widget.