Oh, thanks a lot for that info!
In the meantime I was asking MA(3) about that and they told me that the "Preview-Only" Flag will be set in MA3 and sent out via sACN. But unfortunatley no Data in Preview or BlindMode from MA3.
The "Problem" is, that the vizkey may become a "universal-Parameter-Dongle" if they send out unlimited Parameters via sACN with Preview-flag set (as they do now "virtually" with all normal universes except ArtNet and sACN), because then any sACN Unit which sends DMX data to lamps if the flag is on or off, will then make the vizkey a "limitless-Dongle". That might not be what MA really wants to achieve...
So MA-Users might wait for any Blind-Programming funcionality until they are grey and old or MA is implementing CITP...
A "not to bad workaround" which I received from the Capture Support is, to export the Capture File as MVR into MA3 and use the inbuilt 3D for Preview-Programming if needed so much.