How to invoke Hyper-V Enhanced Session screen resolution prompt?

There's a much easier way - after lots of research! Simple close the VM client down - change the Hyper-V Manager settings (right-hand window of the Hyper-V console), under Server -> Enhanced Session Mode Policy, simply uncheck Allow Enhanced Session mode -> Apply -> Re-check Allow Enhanced Session Mode (this will reset). Now Start the VM in question but don't connect yet. Wait for the VM to start then right-click the VM in the console and you should see "Edit Session Settings" option - click this and the original dialogue will appear again. Done.

You can use cmd.exe and type:

VMConnect.exe <ServerName> <VMName> /edit

P.S.: You can also share local hard drive (Show Options ->tab Local Resources->Local devices and resources->More) as on normal windows remote desktop session :-)