While I don't use the Editor for writing new Chapter's I do find it quite convenient when proof reading or making edits. However, during late evenings and night when I generally get to using it, it seems to cause a lot of strain especially when switching between tabs that are dark (I use the dark theme for the regular site viewing). If you could extend the theme's to the editor page as well I think a lot of us would be very grateful for it. Thanks.
Related suggestion "Dark" and "Sepia": two great options that would enhance the site... (Give the first Post of your favorite suggestions a Like to vote for them and make it more likely for them to get implemented) You could work around that problem with any third-party plugin for your browser which allows manipulating CSS. There is some information about that in the link above. You can also see an example in in this post.
