Can’t connect to computer is usually a pretty bad sign unless you just damaged the port itself. If the bootloader is working then it should at least show up as a serial port (assuming serial drivers present on host machine). If the bootloader and or firmware are corrupt then you won’t be able to connect but you should fix that issue. If usb is hosed or bootloader not there look at threads about how to use st-link (what is it and why do I need it thread). Also physically inspect the board for any burns or signs of water damage or any little triangles of blown out parts on the top of the drv chip it should be perfectly smooth basically, if something in it burns out tends to blow out the top of the chip.
Long story short the st-link will bypass the normal usb connections on the vesc and use serial connections directly on the stm32f4 chip that is the brains on the esc and part you are sending config data and firmware to when you “flash” the vesc. With the st-link so long as the mcu and st-link port isn’t fried you can still connect and flash firmware (I think even use vesc tool to configure but usually I just fix bootloader then do firmware updates etc. from vesc tool over normal usb).