xcode 11 Close secondary editor shortcut

I think SHIFT+CONTROL+CMD+RETURN is exactly what you are looking for (Note: you should be "focused" on left editor to close right).

Helpful link about new Xcode 11 assistant editor behavior: https://www.avanderlee.com/xcode/xcode-assistant-editor/

The shortcut to close the current active editor is:

ctrl + ⌥ option + ⌘ command + W

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