As I said in my first post, you have to use the placeholder [[+wf.classnames]] at the position where you want the class active to appear. In your case probably something like this:
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<a href="[[+wf.link]]" class="[[+wf.level:is=`1`:then=`nav-link`:else=`dropdown-item`]] [[+wf.classnames]]">[[+wf.title]]</a>
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