MacOS – Remap Left Spacebar key on MS Sculpt ergonomic keyboard

Try the DoubleCommand (free, sourceforge) project. According to the features page, you can map the fn key, though it's only listed as partial support. I don't have any personal experience to share...

Sadly, with MacOS Sierra, Karabiner has gone into a strange kind of hiatus-but-not-really-because-someday-we'll-fix-it.

Which is too bad, because Karabiner was the perfect tool for what I needed (which was make MacOS behave like a forty-year-old UNIX terminal because my stupid fingers still hit ^W to delete a word and I kill the window and I can't stop, no, don't help me, I'll die eventually and then my problem is fixed).

My other main tool is Typinator for abbreviations--w for with, h for the, n for and, etc; those really add up.

So far, I've found BetterTouchTool to be a viable replacement for Karabiner, even better in some ways. But worse in others; key repetition doesn't work for me despite the developer saying it does. (Possibly it interacts with Typinator, but turning the latter off doesn’t fix the problem.)

I've written a whole novel using these two tools (Typinator and BetterTouchTool), but I'd appreciate anyone chiming in if they've found something better still.