https://docs.python.org/3/reference/datamodel.html It would appear that the contents index column (left column) should presumably scroll independently, instead it scrolls with the main window in which the content resides until it reaches it's end. This is extremely annoying as it removes the ability to scroll the contents index to jump to a portion of the contents and breaks the convention of user convenience afforded by an independent scrollable index as available for large indexes like APIs. You are intending to maintain visibility of the column when the content is scrolled past the header. As this is the case, in that you are attempting to provide this column for visibility regardless of the scrolling position of the content, as specified, it should: *cease scrolling this column when the content column is scrolled past the header instead of as it is now, when the bottom of the index column is reached.* In addition, independent scrolling functionality to said column in the form of a scroll component or iframe is required.