The new V2 playlist format was introduced with AxUnit V1.5.3721, part of SDK 0.2.395. The old format from earlier versions is still supported but should not be used anymore.
<?xml version="1.0" encoding="utf-8"?>
<AxUnitPlaylist version="2.0">
<test-case parameter="">FullQualified.Test.Name1</test-case>
<test-case parameter="x:=1,y:=2">FullQualified.Test.Name2</test-case>
</AxUnitPlaylist>
As you can see, the playlist is a list of fully qualified test names with test parameters.
Please note that you can only add all argument sets for a parameterized test. It is not possible to just specify a single argument set.