Oops...
I just found this option in Studio workspace properties.
Studio, Tools Menu, Configure Worspace:
then
Configure Workspace Properties, Workspace Preference tab, Table Editor group.
* Table Editor Read-Only
* Allow .int file changes...
I lost when this was introduced..
Maybe worth a note of such options in the DF_FILE_ALLOWED_STRUCTURE_CHANGES doc page for cross reference..
Got my Christmas gift already..
Regards