Define keybindings for R in Visual Studio Code

I'm using Visual Studio Code to write and edit my R-scripts. Therefore I want to create some keybindings like:

nrow(*selected*)

length(*selected*)

So i installed the 'R Extension Pack' (with R & R LSP Client) for Visual Studio. With "ctrl + enter" i could run selected code like this:

{ "key": "ctrl+enter",
  "command": "r.runSelection",                               
  "when": "editorTextFocus && editorLangId == 'r'" }

But how could I run the selection to get the nrow() or length()?