OK, I had to think through what the program is really supposed to do
in a case like this. (Then I had to figure out what it was actually doing,
and then fix it. The fix actually turned out to be pretty simple, but
puzzling out exactly _what_ to fix took a while.)
First off... you're right, UCAC lacks GSC identifiers in any version.
When you click for 'more info' on a UCAC-4 star, you'll get all sorts of
useful data, but GSC identifiers will not be among them.
What's _supposed_ to happen is this:
Turn on GSC labels using the check-box in 'Star Display', and stars with
GSC (and Tycho-2) identifiers are labelled with four-digit numbers. This
should happen no matter what else is going on. Unless you've done some
other trickery with Alt-J/12, this means Guide will show the UCAC stars,
then show _only the labels_ from GSC stars. (This sometimes will result in
"dangling labels", where the star is listed in GSC but not in UCAC-3 or 4.)
Hit Alt-J and enter 12, and Guide will stop displaying UCAC-3 or UCAC-4
stars, and will show the old GSC stars instead, just as if you were still
running Guides 1.0 through 8.0.
All of this works as advertised... _unless_ you have installed UCAC-4.
In that case, Alt-J/12 does not affect the display of UCAC-4.
There's another wrinkle here: Alt-J, then _5_, causes GSC to be turned
off. I'd completely forgotten about this option. But years back, somebody
asked me for it; I think they wanted to make "star charts" without stars
(just DSOs or asteroids or artificial satellites or...)
Hit Alt-J, then 5, and I think you will be able to toggle GSC numbers
back on. Combine that with using the freshly-updated version at
and I think you'll be all set... please let me know if you aren't!