How do I bind a key to open a folder in Visual Studio Code?

You can do this with the following hotkey code, replace C:\Deforum\ with the path you would like to open in VSCode, be sure to use the trailing slash:

vscodepath := "C:\Users\" . A_UserName . "\AppData\Local\Programs\Microsoft VS Code\Code.exe C:\Deforum\"

^!1::
Run % vscodepath
return

I wanted to open the Windows File Explorer's current folder in Visual Studio Code by pressing F9, and this code works for me very well:

#HotIf WinActive("ahk_class CabinetWClass")
~F9::
{ 
    vscodepath := "C:\Program Files\Microsoft VS Code\Code.exe" 
    if !FileExist(vscodepath)
    { 
        vscodepath := "C:\Users\" . A_UserName . "\AppData\Local\Programs\Microsoft VS Code\Code.exe"        
    }

    Send("!d")
    Sleep(100)
    Send("^c")
    Sleep(100)
    command := vscodepath . " " . A_Clipboard    
    A_Clipboard := ""
    Run(command)
    Return
}
#HotIf
Return

• Some explanation: On one machine my VS was in "Program Files", in another machine it was under the user/appdata, so the if handles that situation. The code basically does this: sends Alt+D => to put the focus on the File Explorer address bar, then sends Ctrl+C to copy the path, then combines the VS Code exe path and the current folder to run the command. The top #HotIf WinActive("ahk_class CabinetWClass") makes sure this runs only if the active window is Windows File Explorer, and based on personal experience, if I don't add the empty if at the end, the code execution won't flow to the rest of the AHK file.
• Why F9? Because I'm using F12 for opening the current folder in Windows Terminal, and F11 and F10 are already in use by Windows Explorer.
• The code compiles in AHK v2, and I have not tested it in v1.