I noticed that we can define custom actions in layer list widgets for feature layers, and for map image layer root items. However, you cannot define custom actions for map image layer sublayer items. The createActionsFunction gets called for these items, but any custom actions you add are not added to the node.
Am I missing something or is this a limitation of the LayerList widget?
One more clarification on this issue. Map Image Sub Layer items work okay as long as they are not grouped. Grouped Map Image Sub Layers are the issue. The ConfigureCustomActions is never called for Grouped Map Image Sub Layers so there is no possibility of adding custom actions.