I have to identify the device via SWIM protocol. But I cannot find any information about the existence or structure of any ID register (device ID, part ID, MCU ID, core ID, etc...)
Unfortunately, the information you are looking for is available but protected for industrial reason and cannot be shared.
Some STM8 products have an Unique ID register which can be used (STM8L151x6, for example).
Take a look in th C:\Program Files (x86)\STMicroelectronics\st_toolset\stvd\swim\config\swim_conf.mdb
Retrieving data ...