We know it is doable, but we designed the Docking control to not support this scenario. If we want to enable it we need to do a lot of work. We decision so because nesting docking controls neither look very good, neither user-friendly.
What I could suggest you instead of nesting Docking controls is to use SplitContainers. You could organize your views in such manner that you will not need nested docking controls any more.
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