Hi, is it possible to add a unique key that consists of multiple fields?

You may use uniqueIndex() or index within Table init{} block:

val t = object : Table("t1") {
            val type = varchar("type", 255)
            val name = varchar("name", 255)
            init {
                index(true, name, type)
                uniqueIndex(type, name)
            }
        }