The legend scroll bar cannot scroll with the focus to show the currently focused legend

[leon0leon]

Users cannot see the currently focused legend because the scroll bar does not scroll with the focus when focusing on the legend outside the legend display area. When users use the arrow keys to focus on a legend that is outside the legend display area and needs to scroll to see it, the legend scroll bar does not automatically scroll to display the currently focused legend, as shown in the following two screenshots:
The currently focused legend of the following screenshot is on the next page of the legend display area, and users need to scroll down the legend scroll bar manually to see it:

The currently focused legend of the following screenshot is on the previous page of the legend display area, and users need to scroll up the legend scroll bar manually to see it:

The scroll bar of an ordinary web page can automatically scroll with the currently focused element, making the currently focused element visible on the screen all the time.