Ah, the 1st moment I thought this is a E3Sentry, AKA “AWACS” flying radar disc, as i had 2 days before in Germany. But in magnification of the picture, I see it is a L2J with tail engines.
No idea.
E3Sentries are visible almost daily across Europe because they have some of them located in Spangdahlem. Nothing special with them any longer
They are based in Geilenkirchen (ETNG) 
I got this one flying perfect circles for some hours two weeks before:
It is near Munster training facility, between Hamburg and Hannover.
But, back to the topic … I still don’t understand what the OP meant.
He highlighted the Squawk 7700 US plane with no callsign? Or is the yellow color from TIS-B and not the point here?
I’m glad it wasn’t just me then 
Did i write Spangdahlem? My bad, normally i know it better.
thanks for fixing it.
You can see this pretty often in the area around Karlsruhe/Pforzheim/Stuttgart as well. I assume some sort of training/calibration flights.