as i can see in ktxsoftware repos there is KhaUI. And as i know someone is working on Stablex v2 port to kha. Maybe there are some showcases for that two libraries?

Not sure about KhaUI and Stablex, but there is a working prototype of HaxeUI 2 for Kha:
http://haxeui.org/v2/kha/html5/index.jsp

For some quick debug stuff there is also this little thingy:
https://github.com/luboslenco/zui