jellyfin-web/dashboard-ui/librarypathmapping.html

<div id="libraryPathMappingPage" data-role="page" class="page type-interior librarySectionPage withTabs" data-helpurl="https://github.com/MediaBrowser/Wiki/wiki/Library%20setup" data-require="scripts/librarypathmapping">

    <div data-role="content">
        <div class="content-primary">
            <div class="readOnlyContent">
                <p>${PathSubstitutionHelp}</p>

                <div class="pathSubstitutions"></div>
            </div>

            <br />

            <p>
                Path Substitutions can no longer be added. This feature is being replaced by the network share setup.
            </p>
            <p>
                To configure network shares, edit an existing media library, then click on one of the existing folders. You'll then be able to map a network path to a library path.
            </p>

        </div>
    </div>
</div>