I made an approximate equivilant to RStudio’s default F2 shortcut for VSCode. In RStudio this key opens a function definiton in a new editor tab.

The JSON from my settings.json:

{
    "key": "b",
    "name": "browse function source in new window",
    "type": "command",
    "command": "r.runCommandWithSelectionOrWord",
    "args": "rstudioapi::documentNew(paste0(as.character(styler::style_text(deparse($$))), collapse = '\\n'))"
}

I use a shorcut sequence , c b with the VSCode whichkey extension so your setup will probably look a bit different for "key".

A major drawback of this approach is that since it’s not a saved file, the language mode is not automatically detected, so I have to set the language mode to R to see syntax highlighting etc.

You could also make it show up slightly faster by avoiding styling the code, but I find this is a vast improvement over the default styling.