Currently, topics are ordered based on popularity (number of questions in them) and you cannot reorder them in the "All Topics" page.
It's worth mentioning that only "Collection" topic type is being listed on the "All Topics" page. So if you don't want a topic to be visible on that page, you can simply change the type of it to "Tag".
You can find the differences between Topic types here16.
If this is not enough for your use case, please comment under this answer and we'll be adding this feature request to our backlog.