Thanks chaley, DaltonST
Just spent several hours, in bed, restoring the database -- to no avail
The attached zip contains a csv of the custom-columns table (from DBBrowser). It was one of the first things I looked at, but due to LPS (lockdown perversity syndrome), I interpreted 'editable' values thus: '0' is true and '1' is false'.
But, I've never installed the Zotero plugin, and this is what I have for JS's Protect/Unprotect settings, basically nothing.
If I use DB Browser to change the 'editable' field in the custom column table to '1', I can of course edit the columns, but how did they get set to '0', and why not the ICBM column
Weird.
BR