There’s no way to rename or change type of Relation once it’s created.
Same problem was already reported and solved here: Ability to modify Relation name and type - Bug Reports / Bug Cemetary - Anytype Community
Wow, I feel like I’m having Déjà-vu here 
I’m not able to reproduce this problem, are you sure you’re running the latest version?
Oh, I’m sorry. I got confused. I was expecting that I’ll be able to modify relations directly in the place I created them like I used to do in Notion.
Thanks for instructional video 
Marking as closed as the issue is not really an issue 
Feel free to flsg the topic if you want it to be reopened