With blackmagic probe I've got some python code I currently use in .gdbinit to auto-select the correct com port so I don't have to set it manually anywhere, I would be happy to contribute it.
Before I switched to the blackmagic I could not get my frdm-kl25z mbed board working at all with the onboard cmsis debugger. There was no console outputs from the the debugging engine being used behind the scenes to see what the progress was and the error notification that eventually popped up was very obscure - sorry I don't remember what it was now.
I definitely appreciate the end goal of zero-configuration and having debugging that just works, but in the mean time (especially for beta releases) it'd be great if there was an option to display the openocd / gdb console(s) output when starting debugging, if for no other reason than displaying progress of the debugger connecting.
Currently I hit the debug button, it runs the compiler again (wasting a few seconds as it figures out it doesn't need to compile anything) and then it just looks like it's doing nothing at all while the debug engine is silently starting in the background. Eventually I'm at a debug highlight in the code, or there's a final obscure error message in a notification popup.