I don't understand your last post.
Next to the <global> choice control (combobox/dropdown/etc) should be another control, but in your screenshot is missing.
Are you talking about this problem?
For me everything works fine in ubuntu 17.04... I don't have 16.04 to test at the moment...
I am writing about the drop-down not working well.
In the screenshot with default GTK theme "Ambiance", look at the functions specifications. They have grey color, and for me, very hard to read.
In screenshot with GTK theme "Highcontrast", the drop-down seems to work well for me now.