The preview window is undockable, and closes with the main window by default now. It can be reopened by going to: View|PreviewWindow

The mirror tool is available to speed up concept time! Available under: Tools|Mirror| Horizontally (Vertical coming soon)

The line grid is available now, you can change the color under: Edit|Line grid colors. And you can enable them under: View| Line Grid

Thanks for all the feature requests so far, don't forget this project is funded by donations so anything and everything helps! I can't afford to do this full time otherwise I would. Thanks so much for being so dedicated to this project :)