This was a great idea and it works. On my “disco-board” B-L072Z-LRWAN1 I just needed two jumpers on CN8 removed and I could use SWD pins on CN12.
Additionally, to get logs via serial, I had to add to wires (serial rx and tx) from CMWX1ZZABZ module (pins #23 and #24) to JP6 in B-L072Z-LRWAN1. With that addition I get serial via ST-LINK to virtual COM in PC.