Thank you. This works. However, I can't now work out how to get this working in MB Views, using Twig. What I have so far:
{% for item in post.fieldsetcopies %}
{% if item.libplace %}
{{ item.libplace }},
{% endif %}
{% if item.lib %}
{{ item.lib }},
{% endif %}
{% if item.libshelf %}
. Shelkmark: {{ item.libshelf }},
{% endif %}
<!-- etc -->
{% endfor %}
My 'inputs' (subfields) are not appearing on the list of fields in views.
I've also experimented with for loops on each sub-field in the fieldset.