Add a storefront menu item that opens the wishlist (drawer or wishlist page, depending on Open wishlist settings).
Published guide: Wishlist menu item
shopify://admin/menus.#gatto-wl-details-button

The hash link is a hook the app listens for. It does not need to point at a Shopify page.
In the app, you can also open Wishlist Settings → Open wishlist → Button placement, choose Navigation menu item, and follow the same steps shown there.

In the app, Wishlist Settings → Open wishlist → Button behavior controls whether the menu item opens the drawer or the wishlist page:
