How to change the Event name in an Arranger Track

Sorry, I didn’t mean to be rude (thus the smiley), but it wasn’t clear from your description that you already tried the procedure described in the manual (you’d be surprised how many people forget to search the manual for the simplest procedures…)
Anyway, I used the arranger track just yesterday myself (in C12.0.52 Pro, but its the same in Elements), and it works as described in the link I provided, either click the name of the event in the info bar and type, or opt-click the name in the arranger chain.

If it does not work for you in Elements like that and you think its a bug, you should tag your post with the issue tag and describe how to reproduce it. You could also try starting Cubase in safe mode with
preferences disabled and see if that changes anything.