How to make a button in the top of the screen to be displayed at all times and a button in the bottom of the screen to be visible only when scrolled down?

MIT App Inventor Help
1

How to make a button in the top of the screen to be displayed at all times and a button in the bottom of the screen to be visible only when scrolled down ? I have disabled scroll in the screen1 and used a vertical scroll arrengment layout as the screen displays more than full screen amount of text content

2

Use vertical srcoll handler extension, and use the event when scrolled down and under that put the block to make a floating button visible,