The closest to the ideal I've known so far is Koken [1]. Sadly I can't see any development or maintenance updates since 2017 and it's not open source [2].
Thanks. Unfortunately it's definitely abandoned. It looks like it was sold in 2015 to NetObjects and there's been basically no development on it since then and no support responses or updates. Very sad as it looks like a great app. I wish it was open-sourced
[1] http://koken.me/
[2] http://koken.me/eula.html