What's the story about creating tags??

I'm stymied and I'm curious; I'm new here.

I read all the intro stuff, including the part about creating tags with the # sign.

I included #higherorderthinking in my post, but it didn't show up in the list of all tags.

Two people told me that I don't see it because it's not trending, but doesn't "view all tags" mean that the alphabetical list should contain all of them, trending or not?

Can someone explain to me how this works?

Wondering...