If you get to a point where the changes you just made don’t seem to be working, make sure the prefab you’re working on is saved. With auto-save off, the game uses the last saved prefab when you hit play, even if you’ve made changes. (I just spent 10 minutes debugging my ConfirmTransaction() when the problem was that the onClick hook up wasn’t saved yet.)
I feel your pain. I forget to do this all the time.
After a while, you’ll find yourself in the habit of saving your Prefab as you work on it. Not having Auto Save on is, IMO, a must when working with UI prefabs, especially if they use Vertical or Horizontal Layouts!