Modo de fusión

eliminar el Modo de fusión aplicado a una capa, sin eliminar su contenido.

By @Maggie5F9D

If it's just to remove the blend mode in the layers palette and keep the current blend, maybe this method will help.

main();
function main(){
    var LName= activeDocument.activeLayer.name;
    targetLayer("Bckw");
    executeAction(app.stringIDToTypeID("copyToLayer"), undefined, DialogModes.NO);
    targetLayer("Frwr");
    executeAction(app.stringIDToTypeID("mergeLayersNew"), undefined, DialogModes.NO);
    activeDocument.activeLayer.name= LName;
    function targetLayer(method){
    var d = new ActionDescriptor();
    var r = new ActionReference();
    r.putEnumerated(app.charIDToTypeID("Lyr "), app.charIDToTypeID("Ordn"), app.charIDToTypeID(method));
    d.putReference(app.charIDToTypeID("null"), r);
    var list1 = new ActionList();
    d.putList(app.charIDToTypeID("LyrI"), list1);
    executeAction(app.charIDToTypeID("slct"), d, DialogModes.NO);
    }
}

activeDocument.activeLayer.blendMode = BlendMode.NORMAL

It's really not clear what you mean. Layer modes can easily be switched in the layers palette, but it sounds like you want to actually retain the appearance of a blending mode, which may require extra steps like duplicating the layers involved in the setup before merging/ flattening them. anyway, you need to offer a better explanation of what you are actualyl trying to do.

Mylenium