Other commenters aren't answering this. ctrl+` hides or opens the terminal. If you want to leave it open there's no command to toggle only your cursor focus from editor to terminal.
edit: I take it back, It's just not bound.{"key": "ctrl+#", "command": "workbench.action.terminal.focus"}
But you can't move the focus back with that toggle.
https://code.visualstudio.com/docs/editor/integrated-termina...