I am wondering what does the thickness of the relationship means in my neo4j database. I didn't modify them, but some relationship are automatically visualized in a thick version. Why is it like that and how can I reshape it?
It doesn't mean anything per se, it's just a styling option in browser that you can use to visually highlight or call out different relationships according to whether they're important to you.
In this screenshot, see the "Line Width" option on the right hand portion of the screen, and adjust it for a relationship type however you like