How can I reboot collector box from Debug Console?

I don't think so. You can use `help` to show all available commands and reboot isn't one of them. Wouldn't make sense to put it there either since some collectors run inside containers which don't have a concept of rebooting.

Theoretically, you can run a posh/groovy script from the debug. If you wrote a script to tell the localhost to reboot, that would do it.