Index: src/wp-admin/css/customize-controls.css
===================================================================
--- src/wp-admin/css/customize-controls.css	(revision 39202)
+++ src/wp-admin/css/customize-controls.css	(working copy)
@@ -1168,7 +1168,8 @@
 	font-family: Consolas, Monaco, monospace;
 	font-size: 12px;
 	padding: 6px 8px;
-	height: 553px;
+	height: 500px;
+	height: calc( 100vh - 181px );
 }
 
 /**