Steps to reproduce in 9.0.1:
- Create an empty session
- Create a MIDI event
- Press shortcut to open it in Key Editor
- Switch to the Arrange window, but leaving the Key Editor open
- Create another MIDI event
- Press shortcut to open the new MIDI event in Key Editor
Result: Two Key Editor windows. Can repeat multiple times for even more windows.
The important point is that the new MIDI event was created after a Key Editor is already open. If the events existed before, it works as expected, switching to the already open Key Editor. No duplicates.
Tested on Windows 10.