1) Change ColorDrawable to BitmapDrawable:
Don't forget to add images to the Files tab (in the designer).
2) With anchors. Set the vertical and horizontal anchors to BOTH (see the small white circles):
3) JavaFX sets the minimum height based on the font size. Decrease the font size and it will appear as expected.
4, 5) I will soon write a tutorial about menu items.
6) You cannot add classes in Extra CSS.
Instead create a new css file with this css and put it in the files tab.
Now call:
MainForm.Stylesheets.Add(File.GetUri(File.DirAssets, "1.css")) 'File name is 1.css
7) Yes. Some of these types are only supported by Java 8. Currently B4J minimum version is Java 7.
8) Currently no. You can however combine FXML layouts with bjl layouts.