Everything should be in the database, which is updated once a week. If you want to listen to something specific you can create a favorites list. I don't think there is a system download function like the GRE or older Unidens had.
The Sentinel master database is a download of the Radio Reference database. Thus the Sentinel database is the RR database.
Typically it is updated once a week with the past ones done on Sunday. If you look at the lower left hand corner of Sentinel, you will see a field "Database Version: xx/xx/xxxx".
Butel Software has a couple of programs, ARC536 Basic and ARC536 Pro, which have a feature that will allow you do download data from the RR database for those who are premium subscribers (which I see that you are).