When you first receive the Island Designer app the only permits you have are for laying down dirt or grass paths.
However, you can also create and re-sculpt rivers and cliffs. Of course, these features need to be manually added to your app and, to do that, you need to visit the Resident Services. Head over to the Nook Stop and access the Nook Miles Redemption Catalogue to download the other permits. Larger permits such as the cliff construction permit and the waterscaping application cost 6,000 Bells, but if you want to add more types of path to your library you’ll only be set back 2,000 Bells for each one.
If you’re feeling extra creative then you can purchase the custom design path permit which costs 2,300 Bells. With this feature you can create your own artwork and lay down paths around your island decorated with your unique designs.