custom field based on multiple value field for export

[nindotza]

I have several custom fields that are defined to have multiple values, i.e.
"Text, but with fixed set of permitted values "
"Comma separated text, like tags, shown in the Tag browser"
When I save the epub I notice that the value is placed within a extraneous data, not just the value (see below*). I created a second custom field that is to be a Column built from other columns {#grade} and then look for that metadata after saving the ebook but it is the same not just the one value. What I want is to collect data based on a drop down list or fixed set of values but have a custom field that would extract that one value selected so that it results in metadata such as:

<meta name="calibre:title_sort" content="Alchemist, The"/>

--thanks for any help

*
<meta name="calibre:user_metadata:#grade" content="{&quot;table&quot;: &quot;custom_column_3&quot;, &quot;column&quot;: &quot;value&quot;, &quot;datatype&quot;: &quot;enumeration&quot;, &quot;is_multiple&quot;: null, &quot;kind&quot;: &quot;field&quot;, &quot;name&quot;: &quot;Grade&quot;, &quot;search_terms&quot;: [&quot;#grade&quot;], &quot;label&quot;: &quot;grade&quot;, &quot;colnum&quot;: 3, &quot;display&quot;: {&quot;use_decorations&quot;: 0, &quot;description&quot;: &quot;If epub format has been checked, is it from a scan OCR or retail release with a copyright page? hyphen - means it was newly added. ? means the book description was corrected but the book not viewed and evaluated&quot;, &quot;enum_values&quot;: [&quot;-&quot;, &quot;?&quot;, &quot;scan&quot;, &quot;ebook&quot;, &quot;ebook_fixed&quot;, &quot;retail&quot;, &quot;retail_fixed&quot;, &quot;x_replace&quot;, &quot;x_unavaible&quot;], &quot;enum_colors&quot;: [], &quot;default_value&quot;: &quot;-&quot;}, &quot;is_custom&quot;: true, &quot;is_category&quot;: true, &quot;link_column&quot;: &quot;value&quot;, &quot;category_sort&quot;: &quot;value&quot;, &quot;is_csp&quot;: false, &quot;is_editable&quot;: true, &quot;rec_index&quot;: 25, &quot;#value#&quot;: &quot;retail&quot;, &quot;#extra#&quot;: null, &quot;is_multiple2&quot;: {}}"/>