Myra 0.7.5 is out!
Now it is possible to apply a custom stylesheet in the UI Editor(click on the below animated gif to see it action):
Also issue #40 had been fixed, @SNaidamast.
Link to the latest binary release(it contains ui and stylesheets demonstrated at the above gif): https://github.com/rds1983/Myra/releases/download/0.7.5.146/Myra.0.7.5.146.zip
NuGet had been updated as well.