Its a little thing, but i like how you literally don't need to click on any buttons to save / create a new one / etc. I also like how you can create your own customized path to help you remember the link... just type in a new path and start editing, and you now can share that custom URI.
I think its important to create as little friction to usage as possible, and you've done that.
What's cool is that feature was completely intuitive and you didn't need to point it out. Again, a little thing, but the little bit of delight users experience when they "discover" these types of features goes a long way.
I also like the URL feature, but unlike the other person I did not intuitively expect to type in a a random url and have that work. Its not something people typically do. That said, its pretty cool. You should edit your how to use to include that.
I think its important to create as little friction to usage as possible, and you've done that.