Currently, there isn't a way for me to catch certain events or check for certain player states.

• Player "throws" a trident with the riptide enchantment
  • This is because the player doesn't actually throw it, so no ProjectileLaunchEvent occurs.
• Player is "riptiding" (the state in which the player is twirling through the air with sparkly effects and stuff)

Additionally, it might be useful to offer something akin to the EntityShootBowEvent class, maybe called EntityThrowTridentEvent, with similar methods.  This would make it a lot easier for plugin developers to work with the newly added tridents.

Ref: https://www.spigotmc.org/threads/listening-for-trident-throw.331434/