I'm configuring a new ES 7 cluster for our Analytics team and discovered that the ability to switch dashboards between light and dark modes has been removed in favor of a "global" dark mode setting for each space.
Please consider re-introducing this feature, as it was very helpful in the 6.x product. For example, some of our users prefer light mode for reading text (e.g. Discover) and dark mode for visualizations. The ability to set this at the dashboard level was a great feature in our opinion. (Switching back and forth between spaces for the sake of color is kind of a pain.)