You can only export to excel from a playlist that is made up of tracks added to it from library content. That means you need to add the albums to Roon first, and then to the Playlist, and then it will be exportable.
However, saved Daily Mixes and imported to Local Qobuz mixes are only made up of non-library titles, EVEN IF, you have that album in your library already, the track was added to the playlist from a non-library source.
If you are looking for Roon to “export” just a playlist file, regardless of content source, then that would be a Feature Request.