Hi there,
As far as I know (at least in Linux), you cannot, in the REPL, use the mouse to move around at all. It does not matter whether, as seems to be your case, you are using VSCode’s built-in terminal, or if you are using the REPL in a pure console (outside VSCode). When in the REPL, I advise you to really get used to some key bindings or shortcuts, such as Ctrl-A or Ctrl-E; watch out, however, that these might depend on whether you are within VSCode or outside of it. For me it was really worthwhile learning some of these shortcuts!