QuickDesigner: Some commonly used keyboard shortcuts do not work (correctly) with integrated editor

Steps to reproduce:

• open a Qml file with Designer
• open the integrated Editor
• try to
  • Shift+Delete  (does nothing)
  • Win+cursor keys (macOS uses these for StartOfLine, EndOfLine, StartOfDoc, EndOfDoc, but they seem to get "stolen" by the Navigator widget)

Note: Stealing of the keyboard events might be the more critical thing as this is capable of reordering the items (move up, become sibling,...)