> I see that the comments are from years ago. Are there any ongoing efforts
> to expand the default search set? (Or alternatively, to implement the
> +hackage modifier mentioned.)

It's actually implemented as +nameOfLibrary. Hoogling for "rstrip +missingh" gives:

rstrip :: String -> String
MissingH Data.String.Utils
Same as strip, but applies only to the right side of the string.

Janek