There is a way, if you search the idea, but don't actually go into it, but right click and copy the link it will come in the right format, like https://renxt.ideas.aha.io/ideas/RENXT-I-9947 - you can't share the url when you are already in the idea, although you could probably build it in this format. HOWEVER I agree that the way to share should be made clearer and you should be able to do it within an idea as well.