VSCode – Manually Selecting your Upload (COM) Port
Sometimes when you have multiple COM ports VSCode needs to be told manually what COM port your printer is on. This will show you step by step how to identify the printer COM port and enter it into the Platformio.ini file so you can flash your printer firmware over the USB port. This is common for the 8-bit boards as most 32 bit boards use the SD card for flashing.
If you are missing the Platform IO Toolbar see here on how to restore it: VSCode – PlatformIO Toolbar Missing – How to Fix