What do you man by “import peripheral information”?
To use the board in PlatformIO, a board definition is needed and the framework needs to support the board.
Start with a board definition of a similar board (e.g. https://github.com/platformio/platform-ststm32/blob/master/boards/nucleo_l4r5zi.json or https://github.com/platformio/platform-ststm32/blob/master/boards/nucleo_l496zg_p.json) and make the necessary modifications, i.e. change things like cortex-m4, -DSTM32L4R5xx, 120000000L, stm32l4r5zit6, STM32L4R5xx, NUCLEO_L4R5ZI, 655360 etc. to fit your board.
"platform": "ststm32", as the second line. Then copy to file to
~/.platformio/boards (or whatever your path to the PlatformIO installation is).
Your board should now be available in PlatformIO. Whether it works is a different questions. The STM32L552 looks like a rather new line of MCUs with a different ARM core than other STM32 chips. If you are unlucky, PlatformIO’s STM32cube package might not include this line yet. And the .svd file might also be missing, causing some problems in the debugger. Give it a try anyway.