I'm with Gatobrit all the way here.
There should be a way to add (and simultaneously shuffle) a selection of tracks to "Playing Now" without reshuffling the order of "Playing Now".
MJ's current attitude seems to indicate that the it does not condsider that the user has thought about the order of "Playing Now".
A critical point here, I believe, is that "Playing Now" is quite often carefully and deliberately ordered - often with considerable investment of time.
Hence that order should never be tampered with except by an explicit user directive.
I often have a album playing (in it correct order), but while browsing my library I see some tracks that I think, "And after this album play I'd like to play those, randomly."
As it stands there is no simple way to do that.
To achieve that I have to add them to "Temp" playlist, go to that playlist, shuffle it, then "Add to PLaying Now"