How to integrate a Teensy 3.2 into the IDE 2.0?

PJRC only describes the integration into the classic DE 1.8.x.

It is not possible at this time, but everyone is working to make it possible in the future.

Information about it in this feature request and the ones linked from it:

The classic Arduino IDE never provided the support for what Paul requires, which resulted in the Teensyduino approach where the official Arduino IDE is significantly modified. This time around, we have the opportunity to provide those capabilities out of the box, both for Teensy and for any other boards that might have a use for them. This very complex infrastructure must be designed and implemented properly and that has taken a lot of work. But it is coming along very well.

If you're curious, you can see the RFCs here:

and the work in progress here:

(Arduino CLI handles all the non-GUI operations for all the Arduino development software, so anything like this must first be implemented in Arduino CLI, after which it propagates to the IDE)