The new system is called Smartthings Edge. It uses the lua language rather than groovy. At the moment it doesn’t work through the IDE. See here, for example.
@veonua has developed a driver which works with many, but not yet all Xiaomi switches. In particular it doesn’t yet handle the 3-gang switches. However, I have a copy of his code, which I’ve been experimenting with and which I could update so that you could try it, if you are interested.