Data for K. Čerņevičs, O.V. Yazyev, M. Pizzochero, Phys. Rev. B 102, 201406(R) (2020) DOI: 10.1103/PhysRevB.102.201406 URL: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.102.201406 The following zip file contains: 1)RawData: -Folders for Graphene nanoribbon (GNR) quantum dot (QD) systems classified by lead width n=5,8,11 and subfolders classified by QD widths 5≤m≤13. Each subfolder contains transmission DAT file for QD lengths 2≤L≤50 and a corresponding plot in a PDF file. -Additionally, for n=5 and m=10,11,12 we share eigenvalues for the isolated dot in Eig folder and the transmission DAT file for weakly coupled leads with QD lengths 2≤L≤50 in the 0.2t-0.8t folders. 2)XmGraceFigures -AGR files for editable figures 2-5 as seen in the publication All numerical calculations were carried out by Kwant 1.4 and revised version of TBETA (doi: 10.24435/materialscloud:av-24) code.