Adding layer to open ArcMap document using ArcPy?

I have created a script. I'm run the script using ArcMap and a layer should be added to the open ArcMap document.

I have earlier used MXD.save() witch work fine when I'm running the script outside ArcMap (through an IDE).

How can I change the code below such that the layer is added to the open ArcMap document?

Code:

MXD = arcpy.mapping.MapDocument(r"C:\Users\mgv\Desktop\Koncept\Koncept.mxd")
DF = arcpy.mapping.ListDataFrames(MXD, "Layers")[0]
arcpy.MakeFeatureLayer_management(in_features=line + "_autodimensioned", out_layer=line + "_autodimensioned_layer")
layer = arcpy.mapping.Layer(line + "_autodimensioned_layer")
arcpy.mapping.AddLayer(DF, layer, add_position="AUTO_ARRANGE")

# Add symbology for the layer showing the pipes, symbology for the pipe_type_sup field
updateLayer = arcpy.mapping.ListLayers(MXD, "C:\Users\mgv\Desktop\Koncept\Network.mdb\Network\line_autodim_autodimensioned_layer", DF)[0]
sourceLayer = arcpy.mapping.Layer(r"C:/Users/mgv/Desktop/Koncept/Symbology_configuration_layer.lyr") #task: aendre
arcpy.mapping.UpdateLayer(DF, updateLayer, sourceLayer, True)

# Add label with the pipe type for the supply pipe (DN)
lcs = updateLayer.labelClasses
lc = lcs[0]
lc.expression = "[pipe_type_sup]"
updateLayer.showLabels = True

MXD.save() #Works if running in PyCharm / running the code outside ArcMap / ArcGIS for Desktop