Yes, we were streaming for 24h about Liferay DXP and Liferay Portal 7.3 (and previous versions). All kinds of technical information that might be of interest for you. You might have missed it, but luckily we have it all recorded - and the recordings are available for you:
The audience are developers that have had the "pleasure" of writing custom Item selector views.
For 7.3 we've added a new API (ItemSelectorViewDescriptor) that simplifies a lot the process of adding item selection functionality for any kind of content. It is mostly declarative and removes the need to write a custom JSP file.