Index: editor.css
===================================================================
--- editor.css	(revision 52256)
+++ editor.css	(working copy)
@@ -105,6 +105,9 @@
 figure.wp-block-gallery .block-editor-media-placeholder.is-appender .block-editor-media-placeholder__button {
   margin-bottom: 0;
 }
+figure.wp-block-gallery .block-editor-media-placeholder.is-appender .components-button {
+  margin-bottom: 12px;
+}
 figure.wp-block-gallery .block-editor-media-placeholder {
   margin: 0;
 }