Yes, I used it inside Custom Keyword’s implementation, because that’s what docs says:
(“Mark a keyword to be failed and continue execution”)
https://docs.katalon.com/javadoc/com/kms/katalon/core/util/KeywordUtil.html
So I am now very confused, when you said, it is supposed to be used inside TestCase. If you are right, then the documentation is dumb. even the name KeywordUtil totally suggest, that this class should be used inside Custom Keyword’s implementation 
Are you sure in what you are saying?
I tried to throw exception, and it marks whole TestCase as failed, but marks my Step (my custom Keyword) as passed, even if it throws exception.
To be honest, I sometimes wonder, what were the thoughts of Katalon Developers, when they were implementing this. There is no way how you can do this Steps-Substeps pattern, which is absolutely logical way of doing it, even they implemented it in their custom keywords, that’s why sometimes, you can expand step in LogViewer and see substeps, but it’s not possible to do it in my own keywords?
And how come throwing an exception won’t mark that step as failed? That’s totally weird and I read many other posts, where people had a problem with this, that Step, or even whole TestCase is marked as passed, even though it definitely should be marked as failed. Even writing “assert something” won’t make TestCase failed…
Like almost nothing seems to be working in a good way here in Katalon Studio, I start to be demotivated…
When you want to use data binding, it’s binding everything as a String, so I had to create my own workaround to be able to use something else, than just a String…
How come you guys use Katalon Studio, when it has so many problems?