I can retrieve a subset of submissions with: https://kf.kobotoolbox.org/api/v2/assets/<id>/data/?query={"pat_gruppe/pat_name":"Luk"}&format=json
But this gives fields out-of-submission order, and without labels.
I also can download all submissions of a form as a csv file, with nice labels and in-order, but I have not been able to restrict the download by a query, which leads to huge downloads when I want to create a per-submission report that looks similar to the input forms.
Similar question (without response)
Some more questions on the subject by @iker.montes