You could save data by cookies (Custom code solution only). And than set the Expires Attribute (The maximum lifetime of the cookie). Set 30 for example (30 days).
There are two different types of cookies - session cookies and persistent cookies. If a cookie does not contain an expiration date, it is considered a session cookie. Session cookies are stored in memory and never written to disk. When the browser closes, the cookie is permanently lost from this point on. If the cookie contains an expiration date, it is considered a persistent cookie. On the date specified in the expiration, the cookie will be removed from the disk. read more
"THE PROBLEM" - Users could use the same site on mobile/desktop - must of the wishlist out their based on membership area (And webflow missing this feature). Could be solved by third-party plugin/tool (Like memeberstack and so on).