There are 23 of them in the demo files, although it's impossible to see all of them in one game. From what I can see, they're all from EU3.
The East Indian Trade Route modifier gives a 20% trade boost to a European country that discovers India.
There are "holy land" bonuses for Christians owning Mecca and Jerusalem, and for non-Christians owning Rome. No bonuses for Muslims owning Mecca, though. Orthodox Christians can get a bonus for restoring all 5 patriarchates (Constantinople, Rome, Alexandria, Aleppo and Jerusalem).
The "Western Arms Trade" bonus is back for non-western countries that have excellent relations with a neighbouring western country.
There are "Time of Troubles," "Revolution" and "Peasants War" modifiers that are related to the events of the same names.
There are another 3 modifiers for the late-game Revolution event series.
Catholics can get the "Crusader" and "Excommunicated" modifiers.
Native Tribes that grow large can get 3 different modifiers to punish them - the only way to avoid it is to have a really amazing monarch.
Spain and Portugal can get rid of the Barbary pirates, gaining a nice bonus to their navies, if they own two key provinces in North Africa.
The Chinese get three - a bureaucracy modifier that basically nerfs Ming big-time (17 different penalties to everything from technology to war!!) as long as they have any factions at all. Geez. Plus two for the Mandate of Heaven and losing it. Nice update there - the Ming automatically lose the Mandate of Heaven while they are westernizing.
There's a new modifier for members of the Holy Roman Empire, if it expands to include 25 members. In other words, a strong empire that protects smaller countries instead of blobbing. It gives a nice little bonus to all members.
There's also a single modifier for Scotland that helps them survive against the English in most games.
