The slide for viewing the emails is way to sensitive and hard to control and position. Also, too small a column, it is hard to locate at times. Like your product but improving the size and accuracy of these slides would be a great improvement!
Thank you.
The scrollbar is much improved since earlier versions of the Modern Theme, where it was ridiculously narrow.
If it is still too narrow for you, change to a different Theme that has wider scrollbars. You can select Themes in Menu > Tools > Settings > Appearance > Themes.