All in the interests of a fair trial I think, past offences are not admissible as being prejudicial to the accused
They are sometimes admissible under long established exceptions. It tends to depend on whether the judge thinks probative value outweighs any prejudice.
So for example, evidence that CB broke into holiday apartments might be seen by a German Judge as probative that he broke into 5a. Still better if it could be shown he did break ins at OC before.
But by itself, mere evidence that CB did break ins, it not probative he broke into 5a.
That's where the media usually goes off the rails.
e.g CB gets accused in the MM case, therefore he is suddenly 'linked" (by the media) to the IG case. Of course investigators will look at it, but the mere propensity of itself, does not make it more likely he abducted IG.