I love the addition of dark mode. My eyes have been very grateful this past week
One further improvement would be to have the document canvas color change based on your setting rather than be a saved value specific to the document. This way if you’re on light mode you’re seeing the canvas as lighter, and darker on dark mode. You could still keep the ability to override the canvas color, but also have a button to reset to the UI theme default.
This raises the question related to content, specifically text, that would become inaccessible. You already shift the color of frame labels depending on the canvas color.
You could adjust all the text that is on the canvas without being in a frame to have a similar behavior as the labels for frames. If content is in a frame, however, it wouldn’t shift based on the UI setting.