I created a legend, then changed the symbology of one of my layers. I used the Expression Builder in the Symbology pane to create custom symbology and the layer disappeared from my legend. It is listed in the legend tree in the Contents pane, but isn't showing up in the legend. I deleted the legend and recreated it, and the layer still isn't showing in the legend. Any thoughts?
You can drag and drop a map from the Catalog Pane onto a layout view. You should also be able to drag and drop a feature classes and layer files into an activated map frame. I'm not exactly sure when this functionality was available, but I tested on 2.2.1.
Another thing to keep in mind about adding layers into a legend - the layer must be from the same map/map frame that the legend points to. You will not be able to add a layer from map "A" to a legend that references map "B".