Maybe "wish" isn't a fully accurate word, but I have a few that come to mind.

Sibling Day. Like Valentine's Day, Father's Day, or Mother's Day, but for your siblings. I have had a fluctuating bond with my siblings and this would've been a nice thought.

Friendship Day. We technically celebrate it, but in a rather underwhelming way. There's an annual "friendship festival", but when you go there, they say something like "happy day of friendship between our nation and our Northern neighbors", so it's in a different sense. Might as well go the whole way.

Deganawida Day. This one requires explaining. One day from now, 882 years ago, a great nation here was founded, an empire of righteousness, health, and power. It was of course conquered, but it still culturally resonates. The name of the holiday would be after its founder and the form of celebration would be similar to a day of interpersonal goodwill and local patriotism. Considering the way society is, it would be a nice fix. If added to the calendar, it would also give the lonely month of August its own holiday.

Michaelmas. I grew up with Michaelmas. I still observe it. Why do we shirk it? Cuz some guy who famously nailed a decree on a church door said so? I'm more annoyed people actively avoid it.

Hawaiki Day or whatever you want to call it. I'm surprised we have a day of the year for Christopher Columbus because the Italians voted it in and one for Leif Erickson because the Norse-loving folk voted it in and not one for the Polynesians who discovered South America before the Vikings discovered North America. It's only fair.