The initial set of events so far can be found in this
This will be merged in the near future so if you have a MOD for 3.0 and wish to continue development for it for 3.1 please request the required events (new term for hooks) in this
forum as per the guidelines
Once this PR has been merged events will still be accepted into the core, however you will have to wait until the next phpBB 3.1 release to make use of them. The quicker you request the event, the quicker you can work on porting your MOD to a 3.1 Extension.