I have an existing Kaltura Object Rewrite in a page with a playlist

Is there a way to set the initItemEntryId in the legacy Object Rewrite? Is it called something else?

If it isn’t possible, do you have an example of how to convert the legacy Object Rewrite into a kWidget embed?

In the legacy V1 player, the same property should work. Take a look at this test page:
http://kgit.html5video.org/tags/v1.9.3/modules/KalturaSupport/tests/PlaylistInitItemEntryId.html
The initial entry setup works on both the HTML5 and Flash players.