I've been using Xenko for awhile now. It's a great engine and I love having the ability to use the latest C# and .NET features. Coming from Unity, one of the biggest things I miss is the "play in editor" mode with live editing and viewing of component properties. This last weekend I decided to see if I could build something similar for Xenko. I've managed to complete a proof of concept. Currently it is able to keep track of all the entities in the scene, their components, and the component properties. You can edit the component properties and they change in the game in real-time, and when the game changes the values, they update in the editor view in real time. I'll be throwing this up on Github sometime this week. Setting this up in a project should be pretty easy. Just add a reference to the DLL in your Windows project that launches the game, and then add two lines of code to the Main method for starting up the live editor with the game.
I've attached a screenshot of what it looks like at the moment. I'm pretty bad at UI design, so forgive the ugliness.
Edit: this is on GitHub now - https://github.com/treplogle/XenkoLiveEditor