Actually, there is one "Master page" tab for the root of the content tree. However, if you want to have different page layouts, you can use the ability of the Portal GUI to control inheritance of page templates and content. Detailed info can be found in our tutorial at:
http://devnet.kentico.com/docs/devguide/visual_inheritance.htmIt is also bundled with your Kentico
CMS installation.
Using these tutorials, you can create following site structure (for example):
Root
-> normal page 1
-> normal page 2 (inheriting template/content from "root")
....
-> different section 1 (not inheriting template/content from parent - "root")
-> -> different page 1.1 (inheriting from parent - "different section 1" page/menu item - but not "root")
-> -> different page 1.2 ...
....
-> different section 2
....
According to the tutorial, set "Do not inherit any content" on the Properties/Template tab for "different section" (You can choose the way how to control visual inheritance according to your needs, e.g. no inheritance or inheriting from simple or blank root master page...). "Different section" page will have layout different from "Root" or some "normal section" with "normal page(s)" as subpages, in case you want multiple layouts. All "section" pages will contain page placeholder. All subpages/subsections will be inheriting content from appropriate parent pages.
This way you can achieve multiple Master pages layout.
Best regards,
Ivana Tomanickova