Shared and hidden Spaces will not be visible on your Stories sidebar by default. In order to access those hidden Spaces, click "More Spaces" and select the Space(s) you'd like to appear on your sidebar.
Updated
<% if (previousArticle) { %>
<% } %>
<% if (items.length > 1) { %>
<% if (previousTitle) { %>
<% } %>
<% if (nextArticle) { %>
<%= previousTitle %>
<% } %> <%= previousArticle.title %>
<% if (nextTitle) { %>
<% } %>
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