I can't find anything about their process.

There's really not much about it, the UN page is here: https://www.un.org/en/global-issues/gender-equality

Mostly they seem to have conferences every decade or so and occasionally declare a "International day for X". Seems like a PR kind of thing to me.

But at any rate it's a bad look for the UN. Indicates a dysfunction in the organization that whatever process they have allowed this to happen. I mean it looks like it's a PR campaign that actually makes them look bad. If Guterres was competent he'd shut the thing down entirely and start another one that didn't suck. But since he's an idiot and he will probably just say it's somehow Israel's fault.