It’s a bug. It happens a lot. In the menu, go to
Window -> Katalon Studio Preferences -> General -> Keys
and filter for “delete”, you will see that the Delete entry has no binding. Simply set it like this:
Unfortunately, it will get wiped again. I have yet to figure out WHAT is wiping it – sometimes it survives for days, sometimes it’s gone within a few minutes of opening KS.
Russ