Hi @peter_2628,
Thanks a lot for sharing all the details, that really helps.
I just tried reproducing this on my end using Illustrator version 29.6.1, and I was actually able to see the glow effect color update live when editing the spot color swatch. Could you please confirm the exact version of Illustrator you are using and your operating system details? Also, please check if this happens in a newly created file as well, just to rule out any file-specific issues.
If the issue persists, please try resetting your Illustrator preferences and then test again. Helpful guide: https://adobe.ly/46reCBk. Just make sure to back up your existing preferences before resetting. The article has steps on how to do that.
Looking forward to hearing back.
Abhishek