Would be really nice if Steam could handle multiple wishlists, here's a few reasons why we might want them:

・People could have a custom wishlist for games they wish to gift to their spouse or children, without needing to "pollute" their own personal wishlist

・People could have a wishlist dedicated to games that they want to play above everything else, so it might contain some 10 titles while their standard wishlist has many hundreds, and they could regularly check on those 10 without too much hassle

・This is my personal reason for wanting it - I study Japanese through games, having finished 83, and I regularly check offers on Japan-made games to decide what to play next. The problem is that now they are mixed with the "rest of the world" games, making this more difficult than it should be.
Filtering for language is not even a solution because many non-Japanese games still have Japanese text, and I don't want to entrust my learning to an often questionable translation.

I'm sure you guys might have more reason for wanting this, and I think it's also in Steam best interest, because if a key tracker site decides to implement this, that site will immediately become the main wishlist tool for many people, taking a lot of traffic away from the official Steam store.