Dynamically move object to boundary of another

Hi,
So I have a Tabs element inside a Slideshow. The content of the Tabs varies with some being longer than others vertically. Unfortunately the Slideshow isn’t dynamic so I have to extend it vertically as far as the longest Tab-content. The problem now is that I would like to have a “back to top” button at the bottom so visitors can jump back up quickly. All good until the tab’s content becomes a shorter. Then I’ll get dead space between the tab’s content and the button.

So how can I move the button dynamically to the bottom edge of the tab element?

Using Wix Classic

Thanks in advance

Right click the back to top button and pin to the screen.