How to add buttons to a side scroller game?

Hello!

I'm designing a side scroller game, a bit like this one. Side scrolling is made with a slider. (I think it's easier to use it with a touch screen this way, instead of a draggable bar).

But is there any way to add buttons to a game like this? For example, the character moves right and explores the level, and finds an object. When the player clicks the object, something happens.

Obviously I can add an object with a trigger, but they do not move along the slider. They are stuck in the canvas in one spot. Any tips?:)