There is an action in IntelliJ - "Choose Boot Java Runtime for the IDE". I first downloaded the Corretto 15 JDK within IntelliJ itself as if I was going to use it as the SDK for a Java project, then it was available to me to select as a boot runtime in that action. Some more details here.[1]
The first runtime I tried was Corretto 17 which crashed on me, and I had to delete some `idea.jdk` file somewhere or other to get IntelliJ to start up again. That file seems to contain which JVM to use when starting IntelliJ, I use Toolbox as well (on Ubuntu).
[1]: https://www.jetbrains.com/help/idea/switching-boot-jdk.html