Are you sure this is what you want? I have Tk apps that have dynamic buttons, but they tend to resize their toplevel window as more buttons are added.

I also use stretchy grids sometimes where the size of the grid cells is a proportion of the toplevel window's size.

Anyway, coming back to your original request, this can be done using a Scrolled HList (an HList is an easy way to get a vertical array of buttons capable of being scrolled).