When viewing file changes (e.g. in Log/History tab), the scrollbars aren't pretty usable. Right now, on files with long lines, i need to scroll to the right to see the commit/ discard button. On big changes i also need to scroll back to the top to see this button.

My recommendation:
Attach the scrollbars (atleast the horizontal one) to the hunk/file view and make a header with filename an the button which uses 100% of the space of the preview window. If multiple files are shown, add a second scrollbar on the outer container.