None of them have invested very much in tooling as far as I know. There are some small sml-modes for emacs or plugins for vim but they only do basic syntax highlighting.

One of the biggest missing things for SML tooling is parsers for SML written in SML. They tend to be written in the implementation language and not exposed as a library. So you don't see SML formatters or documentation generators so much.

There have been a few attempts at this but they haven't seriously caught on.