I have recently installed Autocad 2020 as a standalone installation on my Mac Book Pro.  I want to change the default double-click on blocks to the simple attribute editor as described here https://forums.autodesk.com/t5/autocad-for-mac-forum/changing-double-click-action-on-blocks/m-p/6058... but when I start the CUI Editor, everything is greyed out and I can't see a way to unlock and make it editable. I've done it on previous versions, so I've either forgotten how or something has changed....

The only option is to Duplicate the command and then edit that. But I can't delete the default definition, and on restarting Autocad there is no change in behaviour, so maybe I need to 'tell it' to use the Custom definition somewhere?

thanks in advance...