Can I add a game to my Steam wishlist that is no longer sold in the store?

I add all the games I am interested in playing to my Steam wishlist and then when I am looking for giveaways to enter on SG, I use the wishlist filter. The issue is that people still give away games that are no longer for sale on Steam, but I do not see those giveaways when I go to the wishlist filter because I can no longer wishlist the game.

Can I somehow manually add a game to my wishlist with the game's Steam ID?


Edit: I found this page that talks about using scripts to remove games from you wishlist that are no longer in the store, but I need to do the opposite.

They show this script to manually remove an individual game. Can I just change the word "remove" to something else to add a game? I don't really want to screw anything up since I have been adding games to my wishlist for years and would hate to lose it.

$J.post(g_strWishlistBaseURL + 'remove/', {
    'appid': 0, /* Replace the 0 with the appid of the game you wish to remove */
    'sessionid': g_sessionID
});