Yeah, it’s a bit of a hassle since I’m currently maintaining two GUIs in one application - one WinForms, which runs on Windows, and one GTK which runs on Linux (the one you see above). I don’t have any Windows computers, so I can’t make any changes to the Forms UI beyond code alterations. This makes it kind of difficult to fix issues with it.
I would move to GTK on Windows as well (and I’m hoping to do that in the future), but I haven’t been able to find any web browser widgets that work across all platforms. If it works on Windows it doesn’t under Mac and Linux, and if it works on Linux it doesn’t work on Windows… it’s a pain.