My own solution looks like
{% assign stg = site.data.3478_fachrichtung | where_exp: "search", "search.stg_kurz == page.stg_kurz" %}
{% assign extras = site.data.extra | where_exp: "search", "search.stg_kurz == page.stg_kurz" %}
{% assign extra = stg | concat: extras %}
Not perfekt, but it works for me.
site.data.3478_fachrichtung
is the page.data
Has anyone a better solution?
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