Sorry, I only have Screen Shots right now, due to bandwidth.
The widget in the bottom right can not be moved any more the right, either by drag&drop or by using the movement arrows. If you look at the following screenshot, the area it can’t be moved into is exactly the same area where the navigation bar appears when extending it or where it is all the time when not using full-screen mode.
It is probably a lack of support for true fullscreen, then. It is not that big of a deal as with most games you can use just have the dosbox windows to the right and controls to the left. Only if you need to use several widgets at same time it is more convenient to have them to the right and to the left.
Edit: seems like the images are not working. Here are the links: