Thanks, that’s helpful. I renamed only the darktablerc and data.db files, not the library.db file, before restarting dt - I’m assuming this hasn’t caused an irretrievable error. I cannot say with assurance that the error was in darktablerc only, but I’ll give it a try (restoring data.db and restarting dt).
By the way, in the period since elGordo’s last comment, I have been editing my original darktablerc where it has a miss-match to the newly created darktablerc, which I think might be a possible cause the problem (on no factual basis whatsoever). It seemed to me that it would very help if I could change any line in darktablerc to make it a comment. Is this possible?
I have now done this and am greatly pleased to see that all those things which I thought were lost (metadata, tags, styles, scripts and so forth) are restored AND the ‘hover’ issue is fixed. I assume therefore that the issue was indeed within darktablerc. Is this a valid assumption? And if so, would somebody in the development team need to be notified? My problem there is that I don’t think I have any useful data supporting or assisting with defining the problem - do i ? All I can say is that deleting darktablerc and restarting dt fixed the issue, which doesn’t seem to be of much help.
Finally, I should observe that I am very grateful to everybody who contributed to resolving this little-melodrama-of-no-real-consequence.