I am presently converting some workshops from 4.14-4.15 to version 4.17. In the Window|level panel, the “Summon World Composition” button brings out an almost blank window:
What’s wrong with the editor?
It was working perfectly on previous version. Even on 4.16, the window was white but the plus icon was there.
I found the problem.
In the world composition window version 4.17, the graphics of the layer seems to have a Z of 0.0 (???), like the HUD of the window. But the graphics are at the beginning of the scene drawing so the HUD is hidden (except for the text).
If you zoom out enough with the mouse scroll wheel, you’ll get this window or one similar:
Then you can go on with the layers (the HUD is now working).
Thanks for the answer, I was having the same problem and this “fixed” it - in lack of an official solution, that is.
Thanks again 
