[FR] bar_spacing for multiple entities

[ThomDietrich]

Hey all, I'm working with the bar graph function and like the result overall.

The presentation is a bit confusing at times though. Would it be possible to add an option like "bar_spacing_group" in addition to bar_spacing for a more sorted view? Here is an edited image for illustration of the idea:

Anyone out here with the right experience to work on such a feature? Thanks!!