Canvas Hide / Show with 3 clickable Objects

Hello everybody,

I have a problem and could need some help. I'm a beginner at coding.

Each Object here (Planets + Asteroidbelt) has its own Canvas with Button & Text. I've wrote a script that is able to change between the Objects with MouseOver & MouseExit and it works fine but I want to switch between Objects with Mouseclicking, not hovering. I tried it with void MouseButtonDown(), but the opposite to this is missing, there is no "MouseButtonExit" or sth similar to this.

How would someone expierienced approach this?

My Code is:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class PlanetCanvas : MonoBehaviour {
 
 
     public Canvas TextCanvas = null;
 
 
 
     void Start()
     {
         TextCanvas.enabled = false;
     }
 
     void SetCanvasState(bool currentState)
     {
 
         TextCanvas.enabled = currentState;
     }
 
 /*    void OnMouseDown ()
     {
         SetCanvasState (true);
     }*/
         
     void OnMouseOver() 
     {
         SetCanvasState(true);
     }
 
     void OnMouseExit()
     {
         SetCanvasState(false);
     }
 
 }