Hello @Irapohl Cruz ,

I attach .oml bellow, please check if solve you problem.

I add this to OnRender (using SetBooleanTrue ClientAction to change Boolean var and show button):
const element = document.getElementById($parameters.PopupID);let lastScrollTop = 0;element.onscroll = (e)=>{if (element.scrollTop < lastScrollTop){      // upscroll       return;   }    lastScrollTop = element.scrollTop <= 0 ? 0 : element.scrollTop;    if (element.scrollTop + element.offsetHeight>= element.scrollHeight ){        $actions.SetBooleanTrue();    }}

I don't know you want to disable button, but you can change that later.

Hope this works for you,
DC