In the editor
Select one of the topic buttons
Then Select Parent
You will see a red circle with 4 arrows in the bottom right corner of the highlighted group.
Use the up and down arrows to navigate to the other pages.
Once you have found your topic button you want to move:
Click and drag it to the top middle area and hold it there until you see a faded red arrow pointing upward.
It should cycle through the pages
When it gets to the page you want to move the button to, drop it in the spot you want it and the buttons will swap.