I was pressing F2 on columns with Simple templates… e.g.
{id} and
{identifiers:select(isbn)}
When I press F2 on a column with a GPM template… e.g.
program: select(formats_modtimes('yyyy-MM-dd'), 'EPUB') the Template editor does open. But I don't normally show that and similar columns in the book list.
So, perhaps Simple templates have never been editable from the Book list.
BR