Platform support up to a certain Z height in Ultimaker Cura/G-code
Is there a software that will enable this?


Yes, as of Ultimaker Cura 3.3 Beta, Ultimaker Cura allows you to specify an area which will not be considered for adding supports. In your case you could define everything above 4&nbsp;mm to be excluded from building support structures. 

You can look here for this very new feature, it might be what you're looking for.