In PowerShell ISE, if you need to break the execution of the cmdlet, you need to use the awkward key combination of CTRL + Break. Unfortunately, on my computer (Dell XPS 18), I do not have the Break key. But I find an alternative solution (Ctrl+Fn+Pause) suggested by others, although it is inconvenient. To me, a better way, obviously, is just to click the red square icon on the tool set under the menus in PowerShell ISE, which is equivalent to the keystroke of Ctrl+Break.
Solution:
But wait, I do not have the Pause key on my keyboard either. Well, if that's also your case, you need the On-Screen Keyboard. By default, it is off, not showing in the taskbar. You can search on "On-Screen Board" in the Search box on Windows 8/8.1/10. After you find it, you can make it show up temporarily or permanently. There should be a Pause key on it.
P. S.: If you really want to know all of the built-in shortcuts in PowerShell, you can get them by running the following cmdlets (credited to Shay Levy):
$gps = $psISE.GetType().Assembly$rm = New-Object System.Resources.ResourceManager GuiStrings,$gps$rs = $rm.GetResourceSet((Get-Culture),$true,$true)$rs | where Name -match 'Shortcut\d?$|^F\d+Keyboard' | Sort-Object Value | Format-Table -AutoSize
