When I enter the command
Start-Process powershell -WorkingDirectory \"D:\\folder\"
it opens new PowerShell window with D:\\folder
Here's another example which can be used for opening CMD from PowerShell as an administrator into the current folder:
Start-Process cmd -ArgumentList ("/k cd {0}" -f (Get-Location).path) -Verb RunAs
if used within a script you can use
Start-Process cmd -ArgumentList ("/k cd {0}" -f $PSScriptRoot) -Verb RunAs
If you want to open a new elevated PowerShell session from the current one which is not elevated you can use:
Start-Process powershell.exe -ArgumentList ("-NoExit",("cd {0}" -f (Get-Location).path)) -Verb RunAs
or
Start-Process powershell.exe -ArgumentList ("-NoExit",("cd {0}" -f (Get-Location).path)) -Verb RunAs
when used inside scripts