Q: downloading a list of all purchased material from iTunes

You can view the account's purchase history via your Mac's iTunes : See your purchase history in the iTunes Store on a Mac or PC - Apple Support - that isn't exportable or searchable, all you can do is take screenshots

What you can redownload will show in the Purchased section e.g. Account > Purchased menu option on the current iTunes. Albums no longer in the store or bought from a different country's store, nor will items that you've hidden from the cloud (Hide and unhide iTunes Store, App Store, or iBooks Store purchases - Apple Support)