No doubt your reference to the 'court' is to the one in Braunschweig where CB is presently standing trial charged with five sexual offences.It has been raised in court that BKA has only one investigation into CB.
Meaning that the investigations into these five crimes have been successfully concluded with charges laid.
End of investigation = charges being made = court appearances for CB = the trial ending with a conclusion, due legal process having been observed with the results of five investigations concluded.
This may leave only one BKA investigation into CB.
As far as we know.
There could well be others quietly bubbling away in the background.
CB is not only of interest to BKA.
Scotland Yard still have a recently funded investigation on the go centring on their only suspect CB.
The Policia Judiciaria were still interested enough to constitute CB as the only arguido in crimes against MM in time enough to beat the Portuguese Statute of Limitations.
Which means that if CB isn't tried in Germany there may be other options open.
Unlike CB's defence team three national law enforcement agencies have investigated and seen the evidence against CB.
So I would say it is safe enough to say as you do that BKA has only one case left against CB, the others being well on their way to conclusion one way or t'other.
But there are other options.
Just as one finds it remarkable that investigators of three nations who are privy to the evidence have unanimously made CB their only suspect.