Comment 5 for bug 616129

A progress bar for extensions would require a mechanism for extensions back to Inkscape (which currently does not exist and would likely be useless for most extensions).

Even if Inkscape supported it, Scour decided it will not implement a progress bar anytime soon [1] as most SVG files are processed within less than a second these days.

[1] https://github.com/scour-project/scour/issues/77