DVD Studio Pro - Button Combo question

Make four buttons any size

Name them so you can keep track of what is what in authoring
Set movement options by clicking on the the button/advanced tab/navigation

If a direction(left, right, up, down) is set to not set nothing will happen when the user pushes it.
When the user pushes up for the first time you set the navigation to the second up button.
When the user pushes up for the 2nd time you set the navigation to the first down button.

This is why it is useful to have them named something besides button 1.
Make sure you check all of the navigation for each button to ensure the user can't go somewhere you don't want them to. DSP will auto set directions when you create the buttons.

As far as the unveiling part this depends on what it is unveiling. The second down button will go somewhere when the down arrow is pushed. Whether that is a menu, a track, or a chapter marker is up to you.
Also be aware that you can set a button to have an auto action so that it activates immediately when it is navigated to. You may or may not want this on the 2nd down button.

Everything revolves around the directions of the navigational settings for said buttons.
These invisible buttons can be placed anywhere and can be any size. By naming them you will see the name in the navigational pulldown for each button.

The user could or could not end up in a certain spot on the main menu based on what options you give them.

If they hit up once and all directions except up are set to not set you are controlling where they go.

They can only go up and they can't go back.

If you want all directions except up to go to the 1st visible button of the menu you could

also make that happen by setting it in navigation for that button.

If you make 4 buttons and name them something unique and then look at the navigation for the indidividual buttons it should make more sense. DSP auto sets the 4 directions for each button. Any direction can be changed to any button visible or not by the author.