Currently you cannot step into an "Invoke-Command -cn " statement inside a PowerShell script. It would be great if this worked. Remote debugging is available so it would involve setting up the Invoke-Command remote runspace to run in debug step mode, and then wiring the runspace into the console or ISE debugger events.

Also it would be good to have the console or ISE automatically drop into the debugger if Invoke-Command runs a remote script that stops at a break point.