Opacity of the Continuous panel

Hi,

It may be interesting to add a setting about opacity of the Continuous panel (the gray rectangle in Continuous View). The plugin Advanced Find/Replace for gedit has such a setting:

By default, the Continuous panel is see-through, and in my opinion, it makes it more difficult to properly see the key and time signatures because of the measure behind it, and it's not convenient to edit notes directly behind the panel anyway.

Thanks.