This is not supported yet. Actually a custom keyword is presented as a function, so you just call it directly using method call, e.g:
@Keyword
def isElementPresent(TestObject to, int timeout){
//Use Katalon built-in function to find elements with time out 1 seconds
List elements = WebUiBuiltInKeywords.findWebElements(to, timeout)
//Call getHtmlTableColumns custom keyword
getHtmlTableColumns(null, “”)
return elements.size() > 0
}