I'm afraid I don't have any control over where the publish button is, I'm just a volunteer who helps people use this place!
But, there are other ways of using Mastodon such as apps? They have things laid out a bit differently, perhaps one of them might suit you?
You can search on Google Play for "Tusky", which is a good app. Or you can use the official app, which is just called "Mastodon".
If you don't like them you can just go back to the website, or use both!