As far as I can tell, there are no default shortcuts for this. The shortcuts control panel is helpful with this. Creating a shortcut to launch the terminal is easy. I had more trouble trying to launch Tracker. I wound up writing my own program that opens a new tracker window. Then I could set a keyboard shortcut to launch that program. It more or less works like Windows Key + E does on Windows.
But this solution will not work if you are trying to automate the entire install process, because those settings won’t be set yet.
At what point exactly in the install process are you trying to get to the terminal?
You don’t need to select “Haiku” to get to the terminal. As long as the desktop has focus you can do it.
If you are at the very, very beginning (the language select screen) you should be able to press Enter which will take you to the desktop. Then Opt Alt T to open a terminal.