[senhal]

I've got a library with 4000+ books. There are 2 (useless) custom columns which have generate metadata inside epub and opf files:

<meta name="calibre:user_metadata:#formats" content="{&quot;column&quot;: &quot;value&quot;, &quot;datatype&quot;: &quot;composite&quot;, &quot;rec_index&quot;: 22, &quot;search_terms&quot;: [&quot;#formats&quot;], &quot;colnum&quot;: 1, &quot;kind&quot;: &quot;field&quot;, &quot;is_multiple2&quot;: {}, &quot;category_sort&quot;: &quot;value&quot;, &quot;is_csp&quot;: false, &quot;is_editable&quot;: true, &quot;table&quot;: &quot;custom_column_1&quot;, &quot;#extra#&quot;: null, &quot;display&quot;: {&quot;composite_template&quot;: &quot;{:'approximate_formats()'}&quot;, &quot;make_category&quot;: true, &quot;use_decorations&quot;: 2, &quot;contains_html&quot;: true, &quot;composite_sort&quot;: &quot;text&quot;, &quot;description&quot;: &quot;&quot;}, &quot;link_column&quot;: &quot;value&quot;, &quot;label&quot;: &quot;formats&quot;, &quot;is_category&quot;: false, &quot;is_multiple&quot;: null, &quot;is_custom&quot;: true, &quot;name&quot;: &quot;Formati&quot;, &quot;#value#&quot;: &quot;EPUB&quot;}"/>

I tried to delete the columns from Calibre library, but metadatas remain - the same happens if I export books.
Is it possible to bulk remove them?