This blog post is one of those where I need to make a note of something that is relatively easy but every time I have the need it seems to take me several minutes of click around looking for it.
In the page definition you can specify the page template used for the page. One option for the page template to use is "Use Theme Default".
What is the theme default set to? When you edit the page you can see the templates which are being used under the Templates section in the Shared Components region (3rd column). Also if you edit the application definition there is a region which shows the Template Defaults, yet no links or options to change them.
(removed in 4.2)
From the templates page (via shared components) there is a Default column which will contain a checkbox for the theme which is defined as the default.
Ok, I found what the default is. How do I change it? Seems I always try to find something from the templates page to define it. Edit the template? Nope, not there. Ok, it must be defined in the theme. I go to Shared Components->Themes and then double click the theme name. Bam!!!! I'm back to the templates page with the templates for the theme displayed. Since the template list is narrowed down to a selected theme an extra option is added to the Task menu in the right sidebar, "Edit Theme #". Click the link and you're to the Edit Theme page. Previously I didn't notice the "Edit Theme #" entry in the Tasks menu on the Templates page and would have to go back to the Themes page, click in the "Edit Theme" link in that page's Tasks menu and then select the theme to edit.
Once on the Edit Theme page we can change the default Page theme from the select list in the Component Defaults region.