OK, part resolved. Uninstalled graphene completely, reinstalled, re-created child-theme directory etc. And BINGO! finally get child theme activation link appearing from dashboard. Weirdly, it still thinks the child-theme is for graphene ver 1.5.6 instead of 1.6, but frankly I’ll settle for that.(Since I can see the customisable column width feature I’m assuming that I do actually have 1.6 installed.)
