I'm pretty sure it never showed up again! This was also the only episode they pronounced kanar as kaynar instead of kuhnar. I'd have to look through the episode to be sure, but I think the Cardassian phasers were also a different color than the orange they were in later appearances.
It's always interesting to see how they change things as they see what works. It does make me wonder what the original pronunciation of kanar was though. Did the actor read it wrong, or did they change it!
In fact, the script specified that it be pronounced "KAY-nar": https://www.st-minutiae.com/resources/scripts/186.txt
So that must have been forgotten/changed at some point, or maybe it is the auditory equivalent of "whisky" vs. "whiskey".
Very interesting! I had been planning to look up the episode to see for sure, but I forgot to do it.
The pronunciation they ended up going with rolls off the tongue a little easier for me, so maybe that was the reason. I don't remember the first DS9 episode to mention it, but I remembered it being in 2x21 The Wire, so I looked that up. https://www.st-minutiae.com/resources/scripts/441.txt By this point it had been changed to the more common version.