Scroll & zoom error on vertical writing circumstance

Hello, I am making vertical writing Hangul typeface.
I usually check the lining on edit screen but there’s an issue I wanna ask to fix.
On the vertical setting, there’s a restriction that I can scroll down and zoom.
So when I type long text on it I can only zoom on a few glyphs on upper side.
I have trouble when I should edit glyphs on bottom.
Or, if there’s any way to fix this by myself, let me know plz…

thank you for reading