As noted in another post just minutes ago, I'm in the process of converting some existing custom Geocortex tools to ESRI WAB or JSAPI web functionality.
Geocortex offers the apparently rather popular Themes concept in their framework. It's a way to group a number of layers into a theme and then turn layers on/off by switching from one theme to another. So you'd either pick a selection from a dropdown, or with only two choice toggle between two states to activate (turn on) one group layers, thereby turning the other(s) off. QUESTION: Is there an obvious OTB or available custom widget candidate to do this?
Certainly don't want to make anyone have to interact with the LayerList or TOC to hide or unhide layers. it should be more one-click behavior. I could see how you'd build two web maps from map services in Portal and then flip back and forth between those.