I’ve no idea what caused the problem. I think the reason I could not
dragon drop was described by Christopher: there was no blank space between
two entries in which to move the subgroup.
It looked something like this:
What was needed was moving the subgroup to be a group in the same
alphabetical order. There was no place to drag it.
Serendipitously, while looking at the .bib file I also I learned why the
tabs had changed from those I had previously used: JabRef thought I was
using biblatex. When I edited that line to bibtex and opened JabRef the
number of tabs returned to what I used to see. I had not before noticed the
two choices in the drop down box at the bottom of the first tab on the
So, now JabRef is again working properly for me and I’ve learned more
about using it.