To begin Happy Holidays...kinda late.
Using the layout Browser & queue, the button 'Refresh list" does nothing. I believe in the Shimmer desktop layout it is labeled "Rescan collection".
To refresh the number of songs in the library, I have to close and restart Gmusicbrowser.

It does something, just not what you want :)
It re-filter the displayed list using the selected filter if there is one.
To re-scan the collection there is button to do that in the first tab of the settings dialog.
If you want a button with the same function as in the shimmer layout, you can copy the code it is using, currently it uses perl code as there is no gmb command to do that yet (but it's planned with the commands overhaul).
Let me know if you want to do that and need help.

Thanks. I want to avoid plugging bits of code here and there. I did find out how to rescan the collection in the settings dialog. I'll use that.

Let me say that Gmusicbrowser is 'fun' to use. It offers so many possibilities and choices. I'm still in the process of familiarizing myself with this Awesome player.

Keep up the good work.