I've downloaded the 2.0.0-beta.7 of the new IDE, and I understand that this is written on top of the arduino-cli tool. So is there a way to access the CLI from the IDE installation? At the moment I've separately downloaded the CLI, and added it to my Windows Path.
If I remove my manual installation (but keep the IDE) and then type arduino-cli in a terminal, it doesn't find anything.
You can use it just the same as you would an independent installation of Arduino CLI.
Since you're interested in Arduino CLI, I'll mention that when it is in use by Arduino IDE 2.x, the Arduino CLI configuration file in effect is the one located here:
C:\Users\<user name>\.arduinoIDE
It's not necessary for the average Arduino IDE user to know that, nor even what Arduino CLI is, but people interested in doing more advanced things might find it useful information.