The Search in document tab of the sidebar has been removed. The search box allowing users to search within a document is now available above the Table of Contents (ToC) as follows:
When entering a search query, a panel with results overlaps the ToC. The sidebar DOM for the ToC is now as follows:
<div class="reader-aside-toc-content">
<div class="reader-aside-toc-search-in-publication"/>
<div class="reader-aside-toc-scrollable">
<!-- Toc content as before -->
</div>
</div>