Funnily enough, this is the one thing Steam Input doesn’t actually support. It lets you map controller inputs to m/kb or other controller inputs, but mapping m/kb to whatever else isn’t supported at all. I get why it works that way but a bit of a shame, really.
Edit: The headline confused me but according to the article it does just mean controller > keyboard mappings, so never mind
With the “Xbox Extended Feature Support” option selected, you actually can map individual keys to paddles within steam. The problem is Steam Input/BigPicture has been incredibly unreliable for me within the past few months. I’m just glad I can make changes using the first-party software now.
Edit - saw your edit. Changed the post title to make it a little more clear