https://github.com/NodeBB/NodeBB/issues/5723

less/category.less

@@ -149,6 +149,6 @@
 }
 
 .category-dropdown-menu {
-	max-height: 500px;
+	max-height: 600px;
 	overflow-y: auto;
 }

templates/partials/category-selector.tpl

@@ -0,0 +1,12 @@
+<div component="category-selector" class="btn-group <!-- IF pullRight -->pull-right<!-- ENDIF pullRight -->">
+	<button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
+		<span component="category-selector-selected">[[topic:thread_tools.select_category]]</span> <span class="caret"></span>
+	</button>
+	<ul class="dropdown-menu category-dropdown-menu" role="menu">
+		<!-- BEGIN categories -->
+		<li role="presentation" class="category" data-cid="{categories.cid}" data-name="{categories.name}">
+			<a role="menu-item">{categories.level}<span component="category-markup"><!-- IF categories.icon --><span class="fa-stack"><i style="color: {categories.bgColor};" class="fa fa-circle fa-stack-2x"></i><i style="color: {categories.color};" class="fa fa-stack-1x fa-fw {categories.icon}"></i></span><!-- ENDIF categories.icon --> {categories.name}</span></a>
+		</li>
+		<!-- END categories -->
+	</ul>
+</div>

templates/partials/move_thread_modal.tpl

@@ -6,18 +6,7 @@
 				<h3>[[topic:move_topic]]</h3>
 			</div>
 			<div class="modal-body">
-				<label for="select-cid">[[topic:thread_tools.select_category]]</label>
-				<select class="form-control" name="select-cid" id="select-cid">
-					<option>[[topic:thread_tools.select_category]]</option>
-					<!-- BEGIN categories -->
-					<option value="{categories.cid}" data-name="{categories.name}" data-icon="{categories.icon}">{categories.text} <!-- IF categories.disabled -->([[global:disabled]])<!-- ENDIF categories.disabled --></option>
-					<!-- END categories -->
-				</select>
-
-				<div id="move-confirm" class="hide">
-					<hr />
-					<div class="alert alert-info">[[topic:topic_will_be_moved_to]] <strong><span id="confirm-category-name"></span></strong></div>
-				</div>
+				<!-- IMPORT partials/category-selector.tpl -->
 			</div>
 			<div class="modal-footer">
 				<button type="button" class="btn btn-default" data-dismiss="modal" id="move_thread_cancel">[[global:buttons.close]]</button>