Find Layers and Channels with same name

@rrprec , what is the status of the issue? 

And this one selects all Layers with identical names. 

// selectAllLayersOfSameNames;
// 2023, use it at your own risk;
if (app.documents.length > 0) {
////// collect layers //////
var theLayers = collectLayers ();
var theAdd = false;
for (var m = 0; m < theLayers.length; m++) {
    var thisOne = theLayers[m];
    for (var n = 0; n < theLayers.length; n++) {
        var thatOne = theLayers[n];
        if (m != n && thisOne[0] == thatOne[0]) {
            selectLayerByID (thatOne[1], theAdd);
            theAdd = true
        }
    };
};
};
////////////////////////////////////
////// collect layers //////
function collectLayers () {
// get number of layers;
var ref = new ActionReference();
ref.putEnumerated( charIDToTypeID("Dcmn"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") ); 
var applicationDesc = executeActionGet(ref);
var theNumber = applicationDesc.getInteger(stringIDToTypeID("numberOfLayers"));
// process the layers;
var theLayers = new Array;
for (var m = 0; m <= theNumber; m++) {
try {
var ref = new ActionReference();
ref.putIndex( charIDToTypeID( "Lyr " ), m);
var layerDesc = executeActionGet(ref);
var layerSet = typeIDToStringID(layerDesc.getEnumerationValue(stringIDToTypeID("layerSection")));
var isBackground = layerDesc.getBoolean(stringIDToTypeID("background"));
// if group collect values;
if (layerSet != "layerSectionEnd" && layerSet != "layerSectionStart" && isBackground != true) {
var theName = layerDesc.getString(stringIDToTypeID('name'));
var theID = layerDesc.getInteger(stringIDToTypeID('layerID'));
//var theBounds = layerDesc.getObjectValue(stringIDToTypeID("bounds"));
//var theseBounds = [theBounds.getUnitDoubleValue(stringIDToTypeID("left")), theBounds.getUnitDoubleValue(stringIDToTypeID("top")), theBounds.getUnitDoubleValue(stringIDToTypeID("right")), theBounds.getUnitDoubleValue(stringIDToTypeID("bottom"))];
theLayers.push([theName, theID])
};
}
catch (e) {};
};
return theLayers
};
////// based on code by mike hale, via paul riggott //////
function selectLayerByID(id,add){
try {
add = undefined ? add = false:add 
var ref = new ActionReference();
ref.putIdentifier(charIDToTypeID("Lyr "), id);
var desc = new ActionDescriptor();
desc.putReference(charIDToTypeID("null"), ref );
if(add) desc.putEnumerated( stringIDToTypeID( "selectionModifier" ), stringIDToTypeID( "selectionModifierType" ), stringIDToTypeID( "addToSelection" ) ); 
desc.putBoolean( charIDToTypeID( "MkVs" ), false ); 
try{
executeAction(charIDToTypeID("slct"), desc, DialogModes.NO );
}catch(e){
alert(e.message); 
}
} catch (e) {}
};

// selectChannelsOfSameName;
// 2023, use it at your own risk;
if (app.documents.length > 0) {
////// collect layers //////
var theChannels = collectChannels ();
var theAdd = false;
for (var m = 0; m < theChannels.length; m++) {
    var thisOne = theChannels[m];
    for (var n = 0; n < theChannels.length; n++) {
        var thatOne = theChannels[n];
        if (m != n && thisOne[0] == thatOne[0]) {
            selectChannel (thatOne[1], theAdd);
            theAdd = true
        }
    };
};
};
////////////////////////////////////
////// collect channels //////
function collectChannels () {
// get number of layers;
var ref = new ActionReference();
ref.putEnumerated( charIDToTypeID("Dcmn"), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") ); 
var applicationDesc = executeActionGet(ref);
var theNumber = applicationDesc.getInteger(stringIDToTypeID("numberOfChannels"));
// pixel dimensions;
var theWidth = applicationDesc.getUnitDoubleValue(stringIDToTypeID("width"));
var theHeight = applicationDesc.getUnitDoubleValue(stringIDToTypeID("height"));
var theRes = applicationDesc.getUnitDoubleValue(stringIDToTypeID("resolution"));
var thePixels = (theWidth*theRes/72)*(theHeight*theRes/72);
// process the channels;
var theChannels = new Array;
for (var m = 0; m <= theNumber; m++) {
try {
var ref = new ActionReference();
ref.putIndex(stringIDToTypeID( "channel" ), m);
var channelDesc = executeActionGet(ref);
// collect values;
var theName = channelDesc.getString(stringIDToTypeID('channelName'));
var theIndex = channelDesc.getInteger(stringIDToTypeID('itemIndex'));
var theID = channelDesc.getInteger(stringIDToTypeID('ID'));
/*var theColor = channelDesc.getObjectValue(stringIDToTypeID("alphaChannelOptions")).getObjectValue(stringIDToTypeID("color"));
if (channelDesc.hasKey(stringIDToTypeID('alphaChannelOptions')) == true) {
var theHistogram = channelDesc.getList(stringIDToTypeID('histogram'));*/
//var value0 = theHistogram.getInteger(0);
// if not completely black;
//if (value0 != thePixels) {
theChannels.push([theName, theIndex, theID])
//} else {}
//};
} catch (e) {};
};
return theChannels
};
////// select channel //////
function selectChannel (theIndex, theAdd) {
var desc6 = new ActionDescriptor();
var ref1 = new ActionReference();
ref1.putIndex( stringIDToTypeID( "channel" ), theIndex );
desc6.putReference( stringIDToTypeID( "null" ), ref1 );
desc6.putBoolean( stringIDToTypeID( "extend" ), true );
executeAction( stringIDToTypeID( "select" ), desc6, DialogModes.NO );
};

I'm thinking that such a script would be quite slow.

Have you searched the forum or web for one yet?

EDIT:

Can you post a screenshot of the layers panel? Is this only for top-level layers/layer sets – or do you also need to search inside layer groups and nested layer groups within layer groups?

Wouldn’t it be better to avoid the duplication to begin with if they are the result of some automated processes? 

What are the Scripts/Actions involved in the creation of the duplicate Layers/Channels? 

Could you please provide a couple of exemplary files or at least post screenshots with the pertinent Panels (Toolbar, Layers, Options Bar, Channels, …) visible?