Only flagged photos selectable in Slideshow
I was hastily putting together a slideshow in Lightroom Classic for a family gathering, and wanted the slideshow to include only the flagged (picked) photos. Unfortunately, I didn't see the Filter feature in the lower right corner of slideshow, but I found something else that seemed to have the desired effect. The filmstrip at the bottom shows all the pictures in the collection, but the non-flagged ones are dark grey and can't be selected.
Bur I can't remember what I did to get this and don't know how to clear it so that all photos are selectable in Slideshow. I have tried reproducing what I did with a different collection without success, and I can't find this mentioned in the documentation anywhere. Does anyone know what I did and how to clear it?

