--- a/src/pyams_portal/resources/js/portal.js	Wed Sep 26 17:47:33 2018 +0200
+++ b/src/pyams_portal/resources/js/portal.js	Wed Sep 26 18:35:37 2018 +0200
@@ -298,7 +298,11 @@
 				}
 				ui.draggable.addClass('already-dropped');
 				var row_id = ui.helper.parents('.row:first').data('ams-row-id');
-				MyAMS.dialog.open('add-template-slot.html?add_form.widgets.row_id=' + row_id);
+				MyAMS.dialog.open('add-template-slot.html?add_form.widgets.row_id=' + row_id, {}, {
+					hide: function() {
+						$('.already-dropped').remove();
+					}
+				});
 			},
 
 			startSlotResize: function(event, ui) {