Only 2 places need to update the URL for the pressbook:

1. In the moduleshortcut div – the pressbook link is a menu_book icon.
2. In the iframeholder div – the pressbook link is the main content.

Code:

<div id="moduleshortcut" class="eedunav-pressbook" role="navigation">
<a class="eedunav-btn pbc-popleft external" href="PRESSBOOKSURL" target="pressbook" aria-label="Website version of Pressbook"> <span class="material-icons">menu_book</span> </a>
<a class="eedunav-btn pbc-popleft" href="/courses/298/modules/1992" aria-label="Go to Session 1 Module list" data-api-returntype="Module" > <span class="material-symbols-outlined">checklist_rtl</span> </a>
</div>
<div id="outer" class="iframe-container">
<div id="iframeholder" class="iframe-holder">
<iframe src="PRESSBOOKSURL" loading="lazy" allowfullscreen="allowfullscreen"></iframe></div>
</div>