I was wondering how I setup tabs for my foobar2k for things such as "browse" or "search". I want to have them above the main playlist window.

Use the Uie_tabs2 plugin to get the tabbed panel stack. Add them using the ColumnsUI Layout. They behave in the same way as splitters.

So for browser, i'm guessing the layout will be something like

Tabbed panel
--Horizontal Splitter
---Browser
---Browser
---Browser