The scrollbar doesn't overlay on top of content, even if you set its position: absolute;. Instead, there are few customizable options available for scrollbars, like adjusting the track and thumb colors, changing the height and width, or toggling visibility (using display property). Firefox supports some of these customizations as well.

If you're looking for more control over your scrollbar's appearance, you can either create your own scrollbar (check out this tutorial) or use a library like simplebar, which simplifies the process. If your are using react make sure to use react-simplebar