The new Fibaro micro dimmer 2 does not require a neutral and you can install it behind your existing in-wall switch. Plus it can act as a scene controller too. You can read more about it here: http://www.thesmartesthouse.com/blogs/the-smartest-blog/fibaro-z-wave-plus-dimmer-2-fgd-212-review
And here’s a great custom device handler by @erocm1231 that lets you dig into advanced settings: [RELEASE] Fibaro Dimmer 2 (US)