Add help for each selection
I think it will be good to allow to set a help text for each selection.
It is doable in HTML by setting a title attribute on the option: https://stackoverflow.com/a/11367256/687601
But there is no such mechanism on GTK.
I think it is not a big deal if only sao support this feature as it is only help so it does not prevent any workflow. (Also it is necessary supported by all browsers anyway).