You can link to a topic with just the number: /topic/1. Everything after that is fine. If your browser copy pastes urls like that there isn't much else that can be done.
I want to change my URL of the forum, but it seems to me that the only place we can set it is when setuping it. I am concerning whether the data will be removed when re-setup the forum. Is there any other method?
node app.js --setup) doesn't change any data (at most adds an admin if no one has been added yet). you can safe run it to reconfigure your board
Btw: welcome to the NodeBB community