I currently use Cmder for this, which is based upon ConEmu. There are already two PowerShell tasks and I assume that I can update them to point to my local install of PowerShell Core (in C:\Program Files\PowerShell.0.0).
Você está usando o executável errado.
The binary name for PowerShell Core has been changed from powershell(.exe) to pwsh(.exe). This change provides a deterministic way for users to run PowerShell Core on machines to support side-by-side Windows PowerShell and PowerShell Core installations. pwsh is also much shorter and easier to type.
O que há de novo no PowerShell Core 6.0
Adicionalmente
You can launch PowerShell via the Start Menu or $env:ProgramFiles\PowerShell\pwsh.exe