diff --git a/include/fsm.h b/include/fsm.h
index 2276eae..8cdd8ef 100644
--- a/include/fsm.h
+++ b/include/fsm.h
@@ -143,7 +143,8 @@ enum fsm_enum_log_source {
     SRC_CONTENT, /**< MAIN, APP, WIDGETS, SIGNAL */ MAIN, APP, WIDGETS, SIGNAL,
     WINDOW, /**< MAIN, DIALOG, MODAL, TEXT */
         MAIN_WINDOW, DIALOG_WINDOW, MODAL_WINDOW, TEXT_WINDOW,
-    TOPBAR, /**< LEFT, CENTER, RIGHT */ TOPBAR_LEFT, TOPBAR_CENTER, TOPBAR_RIGHT,
+    HEADER_BAR, /**< LEFT, CENTER, RIGHT */ HEADER_BAR_LEFT, HEADER_BAR_CENTER,
+        HEADER_BAR_RIGHT,
     PAGE, /**< SYNTH, STATE, RULES, [USER TREE], [SELECTED_RULE], MEASURES, RESULTS */
         SYNTH_PAGE, STATE_PAGE, RULES_PAGE, MEASURES_PAGE, RESULTS_PAGE,
     SYNTHESIS, /**< GLAREA, CAMERA, CONTROLS, RESULTS (duplicates from other pages) */
diff --git a/include/widget.h b/include/widget.h
index a379674..35edeb7 100644
--- a/include/widget.h
+++ b/include/widget.h
@@ -31,3 +31,5 @@
 void on_app_activation (GtkApplication *app);
 void widget_design_main_window (GtkWindow *main_window, GtkApplication *app);
 gboolean on_window_close_request (GtkWindow *main_window, gpointer user_data);
+void on_toggle_exec_edit (GtkWidget *btt_XOR_EXEC_EDIT, gpointer user_data);
+
diff --git a/src/widget/main_window/design.c b/src/widget/main_window/design.c
index def7ed1..d426bf8 100644
--- a/src/widget/main_window/design.c
+++ b/src/widget/main_window/design.c
@@ -33,6 +33,20 @@
 #include "../../../include/widget.h"
 #include "../../../include/fsm.h"
 
+/**
+ * every "on_" function is to go in "signal.c" (not yet implemented)
+ *
+ * @param *toggled_button
+ * @param user_data
+ */
+void on_toggle_exec_edit (GtkWidget *toggled_button, gpointer user_data)
+{
+    fsm_add_log (INFO, BUTTON, "signal", "toggle exec edit()",
+        "flip status request + bell 😇️ gdk_display_beep()");
+
+    gdk_display_beep (gdk_display_get_default());
+}
+
  /**
  * @brief Main window design()
  *
@@ -41,22 +55,34 @@
  */
 void widget_design_main_window (GtkWindow *main_window, GtkApplication *app)
 {
-    fsm_add_log (INFO, TOPBAR, "widget/main_window/design",
+    GtkWidget *header_bar = GTK_WIDGET (gtk_header_bar_new ());
+
+    gpointer no_local_data = NULL;
+
+    fsm_add_log (INFO, HEADER_BAR_LEFT, "widget/main_window/design",
                                __func__, "start of design");
 
-    /* GtkWidget *topbar = GTK_WIDGET (gtk_header_bar_new ()); */
-
-    /* char *title = "E coli   (with permission from David S. Goodsell, 2009)"; */
-    /* gtk_header_bar_set_title_widget (GTK_HEADER_BAR (topbar), */
-    /*                                  gtk_label_new (title)); */
+    char *title = "E coli   (with permission from David S. Goodsell, 2009)";
+    gtk_header_bar_set_title_widget (GTK_HEADER_BAR (header_bar),
+                                     gtk_label_new (title));
 
     GtkWidget *e_coli = GTK_WIDGET (gtk_picture_new_for_filename
                           ("./docs/showcase/E coli (Goodsell).png"));
 
     gtk_window_set_child (main_window, e_coli);
 
+    GtkButton *btt_XOR_EXEC_EDIT = GTK_BUTTON (gtk_toggle_button_new ());
+    gtk_button_set_icon_name (btt_XOR_EXEC_EDIT, "power-profile-balanced-rtl-symbolic");
+    g_signal_connect (btt_XOR_EXEC_EDIT, "clicked", G_CALLBACK (on_toggle_exec_edit),
+                      no_local_data);
+
+    gtk_header_bar_pack_start (GTK_HEADER_BAR (header_bar),
+                               GTK_WIDGET (btt_XOR_EXEC_EDIT));
+
+    gtk_window_set_titlebar (main_window, GTK_WIDGET (header_bar));
+
 //    g_object_unref (e_coli);
 
-    fsm_add_log (INFO, TOPBAR, "widget/main_window/design",
-                               __func__, "end of design  ->  present");
+    fsm_add_log (INFO, HEADER_BAR_LEFT, "widget/main_window/design",
+                              __func__, "end of design  ->  present");
 }