Add custom dock plugin

addons/my_custom_dock/custom_dock.gd

@@ -1,12 +1,20 @@
 @tool
 extends EditorPlugin
 
+var dock
 
 func _enter_tree():
 	# Initialization of the plugin goes here.
-	pass
+	# Load and instantiate the dock scene.
+	dock = preload("res://addons/my_custom_dock/my_dock.tscn").instantiate()
+	# Add the loaded scene to the dock.
+	# Left ot the editor, Upper Left (UL).
+	add_control_to_dock(DOCK_SLOT_LEFT_UL, dock)
 
 
 func _exit_tree():
 	# Clean-up of the plugin goes here.
-	pass
+	# Remove the dock.
+	remove_control_from_docks(dock)
+	# Free from memory.
+	dock.free()

addons/my_custom_dock/my_dock.tscn

@@ -0,0 +1,7 @@
+[gd_scene format=3 uid="uid://beaqgns7vwsyt"]
+
+[node name="My Dock" type="Button"]
+offset_right = 40.0
+offset_bottom = 40.0
+theme_override_font_sizes/font_size = 24
+text = "Click My Dock Button!"

project.godot

@@ -16,7 +16,7 @@ config/icon="res://icon.svg"
 
 [editor_plugins]
 
-enabled=PackedStringArray("res://addons/my_custom_node/plugin.cfg")
+enabled=PackedStringArray("res://addons/my_custom_dock/plugin.cfg", "res://addons/my_custom_node/plugin.cfg")
 
 [rendering]