https://github.com/NodeBB/NodeBB/issues/4804

less/category.less

@@ -172,3 +172,19 @@
 	max-height: 500px;
 	overflow-y: auto;
 }
+
+.merge-topic-card {
+	position: fixed;
+	bottom: 10%;
+	right: 2rem;
+	z-index: 1;
+	.topics-section {
+		text-align: center;
+	}
+}
+
+@media screen and (min-width: @screen-sm-min) {
+	.merge-topic-card {
+		max-width: 33%;
+	}
+}

templates/partials/category/tools.tpl

@@ -45,6 +45,11 @@
 				<i class="fa fa-fw fa-arrows"></i> [[topic:thread_tools.move_all]]
 			</a>
 		</li>
+		<li>
+			<a component="topic/merge" href="#">
+				<i class="fa fa-fw fa-code-fork"></i> [[topic:thread_tools.merge]]
+			</a>
+		</li>
 
 		<li class="divider"></li>
 

templates/partials/merge_topics_modal.tpl

@@ -0,0 +1,25 @@
+<div class="panel panel-primary merge-topic-card">
+	<div class="panel-heading">
+		<h3 class="panel-title">[[topic:thread_tools.merge_topics]]</h3>
+	</div>
+	<div class="panel-body">
+		<p>
+			[[topic:merge_topics_instruction]]<br />
+			<div class="topics-section">
+				<!-- BEGIN topics -->
+				<!-- IF @index -->
+				<i class="fa fa-chevron-up"></i><br/>
+				<!-- ENDIF @index -->
+				<span>{topics.title}</span><br/>
+				<!-- END topics -->
+			</div>
+		</p>
+	</div>
+	<div class="panel-footer">
+		&nbsp;
+		<div class="btn-group pull-right">
+			<button class="btn btn-link btn-xs" id="merge_topics_cancel">[[global:buttons.close]]</button>
+			<button class="btn btn-primary btn-xs" id="merge_topics_confirm" disabled>[[topic:thread_tools.merge]]</button>
+		</div>
+	</div>
+</div>