Hi Friends,
I happened to notice a kind of dot at the right border of the Inkscape window, at the end of the tool control bar, and curiosity has the best of me

It's there with every tool, and even shows up when the window is the Restored size (not maximized), which makes me think it's not part of the interface. But really I have no idea. Here's a screen shot with a dark red half circle around it.

What is it? Does anyone know?