How can I configure the SongTree so that the current track is displayed automatically?
By using the follow=1 option, but it will only work the first time the layout is used, as the user setting as priority over the layout setting.
How do I set the VolumeIcon that I can use the mouse wheel to control.
By including it in the VolumeScroll virtual container, though it can be better to include more containers/widgets :
VolumeScroll= VolumeIcon HBexample
How do I configure MainMenuItem that only a certain GTK icon is displayed?
You can't. Though it's true there is a lot of icons. Maybe I could add an option.
I plan to redesign the command system, it should be possible then to recreate the menu completely via MenuItems widgets
How do I configure a HB / VB, so it is not visible when nothing is playing.
You can't, though that is an interesting idea, I'll probably add it.
btw about your layout, I'll look at it in a few days, when I work on the new layouts for the next stable version.