I already wrote about the btLr text direction in the context of Writer table cells as a result of a Collabora hack week. This is meant to be an update to present what happened in the past 2 months. Here is a video showing the results:
I fixed the following problems since the last blog post on this topic:
All this is available in LibreOffice master (towards 6.3), so you can try it out right now, if interested.