Scott,
There is currently no configuration for this but almost anything can be done if you do some coding.
In the Widget.js file find the case "DYNAMIC" and add the following lines(5 thru 12):
if(layer.type.toUpperCase() === 'DYNAMIC'){
if(layer.imageformat){
var ip = new ImageParameters();
ip.format = layer.imageformat;
if(layer.hasOwnProperty('hidelayers')){
ip.layerIds = layer.hidelayers.split();
ip.layerOption = ImageParameters.LAYER_OPTION_HIDE;
}
if(layer.hasOwnProperty('showlayers')){
ip.layerIds = layer.showlayers.split();
ip.layerOption = ImageParameters.LAYER_OPTION_SHOW;
}
if(layer.hasOwnProperty('imagedpi')){
ip.dpi = layer.imagedpi;
}
lOptions.imageParameters = ip;
}
Then in the config_Local Layer Widget.json add either showlayers or hidelayers (showlayers will overwrite hidelayers if you mistakenly add both).
the json property would look like this:
"hidelayers": "0,68,69,79,80,81,82,83"
If you need more context here is a full layer example:
{
"type": "Dynamic",
"name": "Parcels",
"url": "http://someserver/arcgis/rest/services/someservice/MapServer",
"opacity": 0.9,
"visible": true,
"imageformat": "png32",
"imagedpi": 96,
"disableclientcaching": true,
"hidelayers": "0,68,69,79,80,81,82,83"
}