Transfer variables through SWD with Segger J-Trace without using SWO interface?
If you take a look at the device manual Chapter 27 (page 451) you will see that this device supports SWD ( Serial Wire Debug ) which is a 2-wire alternative of a JTAG interface. Using this interface you can access all memories, registers and peripherals of the target. I recommend that you look after OpenOCD application and GDB debugging. To have an idea of what I'm talking about I found this link that can give you a head start.