trilium/src/views/details/search.ejs

<div id="note-detail-search" class="note-detail-component">
    <div style="display: flex; align-items: center;">
        <strong>Search string: &nbsp; &nbsp;</strong>
        <textarea rows="4" cols="40" id="search-string"></textarea>

        <span>
            &nbsp; &nbsp;
            <button type="button" class="btn btn-primary" id="note-detail-search-refresh-results-button">Refresh tree</button>
        </span>
    </div>

    <br />

    <h4>Help</h4>
    <p>
    <ul>
        <li>
            <code>@abc</code> - matches notes with label abc</li>
        <li>
            <code>@!abc</code> - matches notes without abc label (maybe not the best syntax)</li>
        <li>
            <code>@abc=true</code> - matches notes with label abc having value true</li>
        <li><code>@abc!=true</code></li>
        <li>
            <code>@"weird label"="weird value"</code> - works also with whitespace inside names values</li>
        <li>
            <code>@abc and @def</code> - matches notes with both abc and def</li>
        <li>
            <code>@abc @def</code> - AND relation is implicit when specifying multiple labels</li>
        <li>
            <code>@abc or @def</code> - OR relation</li>
        <li>
            <code>@abc&lt;=5</code> - numerical comparison (also &gt;, &gt;=, &lt;).</li>
        <li>
            <code>some search string @abc @def</code> - combination of fulltext and label search - both of them need to match (OR not supported)</li>
        <li>
            <code>@abc @def some search string</code> - same combination</li>
    </ul>

    <button class="btn btn-sm" type="button" data-help-page="Search">Complete help on search</button>
    </p>
</div>