The object is developing using REPL more fast and with ease. How this extension tries to achieve this is accepting a terminal command for opening whatever REPL you use with the options that you want, then you run the desired code from your file with a shortcut.
Set the terminal command for opening the desired REPL in the VSCode settings.
Select some code and run by calling vscode command Repeater (REPL Tool): Run selected code. If you need to restart the REPL, call the function Repeater (REPL Tool): Restart REPL then run selected code.
Repeater (REPL Tool): Run selected code -> Ctrl+i or Cmd+i
Repeater (REPL Tool): Restart REPL then run selected code -> Shift+Ctrl+i or Shift+Cmd+i
The REPL that you going to use :P