Where can I find documentation on what BXML attributes and styles a component supports?

Component attributes are simply the Java bean properties of the component class itself. Styles are the bean properties of the currently installed skin. So, you can simply refer to the Javadoc for the component to identify the supported attributes, and for the skin (generally either in org.apache.pivot.skin or org.apache.pivot.skin.terra) to identify the supported styles. How Java classes map to BXML is discussed in more detail in the BXML Primer.