Example of showing a bottom panel in a Godot plugin

bottom_panel_plugin.gd

@tool
extends EditorPlugin

const control_scene = preload("res://addons/plugin/plugin.tscn")

var control: Control

func _enter_tree() -> void:
	control = control_scene.instantiate()
	add_control_to_bottom_panel(control, "Plugin")

func _exit_tree() -> void:
	if control:
		# Call remove control before queue freeing it!
		remove_control_from_bottom_panel(control)
		control.queue_free()