I use stcube for pin allocation. At the moment I have a project with the STM32F303VD. The recent errata sheet clearly says: "2.1.3 Full JTAG configuration without NJTRST pin cannot be used ." However stcube offers a 4 pin JTAG entry. It would be helpfull, if stcube would gray out the 4 pin JTAG option for devices with the JTAG/NTRST errata so that people will not find out the errata later the hard way.