It doesn't seem like Insert/Overwrite is implemented yet as of Arduino IDE 2.0.0-beta.10
Current behavior: Pressing the INSERT key on the keyboard does nothing.
Expected behavior: Pressing the INSERT key on the keyboard shold change the cursor from a caret to a block, and when you next type, it should overwrite existing characters rather than inserting new ones.
Works fine in Arduino 1.8.
Other than that the upgrade has been fantastic, it immediately picked up all my existing platforms from 1.8, and auto-complete is incredibly useful!