Thank you for tour reply!
I think that the URL of a published report/dashboard is always the same (also if the group in which it's shared changes or the report recevies an update), but I'm searching for a confirm by someone that does know it certainly.
Anyway I see two ways to implement this thing:
1. it's the way that you've mentioned of custom visualization
2. it's not so nice, but it's possible to insert a link in text boxes