Windows: Windows 10 Home -- 20H2 -- Build 19042.1083
If you open a viewer (e.g. in the opposite pane) and you want to use the whole pane as a viewer a bit of the treeview is visible. See screenshot.
However, this only happens if you drag the top of the Viewer to the bottom (or even above) the file path too quickly.
This doesn't happen if you do it slowly, bit by bit e.g. first half of the pane is used for viewing and you set it slightly bigger until it reaches the bottom of the tab.
