I suggest that you send your enhancement request directly to the JMP folks at:
They are in the business of handling such enhancement requests, making sure they get uploaded to the correct group of developers.
Curious, I ran your script, and I also ran show properties(dt);, but couldn't find a Add Multiple Columns option in the show properties? Beyond this, I feel the method described above is more to help a programmer remember syntax while a show properties command is helpful in learning what options are available. It's also more useful since comment text are included describing a function might do.
Possibly a right click, Show Properties option that will open the scripting index to the appropriate page? Like the above would send me here:
If this was implemented I would definitely want a hot key for this, maybe Ctrl+Shift+Space?