KSP 1.12.x - the ingame editor function does not work correctly

[caerfinon]

In the recent KSP upgrades to the 1.12 versions, The editor feature of Kerbal Konstructs no longer functions correctly.
When CTL-K is pressed from the flight screen the following occurs:

• The Statics Editor displays as expected
• Navigation to the other menu options (Spawn New, Edit MapDecals, Edit Groups, Export, Save) produce either no effect or unexpected actions
• From the Local instances page if you select one, the edit window either does not display or only a blank grey box appears with no usable functions. This behaviour repeats in the MapDecals and Groups page, if you mange to navigate to them and select an item to edit.

In-Game play appears to be unaffected, existing statics, launch-sites, and facilities appear to be working as they should.