SUPPLEMENTAL INDENTUREDated as of July 26, 2018COMMONWEALTH EDISON COMPANYtoBNY MELLON TRUST COMPANY OF ILLINOISandD.G. DONOVANTrustees Under Mortgage Dated July 1, 1923,and CertainIndentures Supplemental TheretoProviding for Issuance ofFIRST MORTGAGE...