There are now multiple events connected with a manager system to allow historical or ahistorical borders. You can edit almost every country in Europe and Korea/Japan now with them.
They're triggered once you capitulate Japan or Germany respectively and the peace conference is over. Make sure to create an occupation zone (requires Yalta conference) or annex them completely, regardless of your plans! Also the events won't trigger if you are in a war with the Soviets/French/Brits or Americans as one of the mentioned before.

Most events are dynamic by this point and have strict trigger conditions. However, if you try to somehow stay realistic and historical you should get them without problems. Keep in mind that the AI will be able to decide things and can decline offers, though that's very rare.
These ID's are typed in the console which you can open with "^". If you did that, type in the console "event EVENTID" without the quotation marks and the event ID. An example would be "event ne_asia.1" to trigger the Asia manager.


Keep in mind that there are multiple event chains and things can go weird or not work if some prequisites are not fullfilled. Some events for instance are suited to be triggered while playing as a specific nation or after some other event happened. YOU MAY BREAK YOUR GAME BY USING THE CODES WRONG!
The managers and options are usable at any time however.
Anyway, here are the IDs:

[CODES ARE NOT UPDATED ATM]