Hi Peter!
Answering your question #4:

  1. Go to the plain text editor

2. Insert a tag <iframe> with embeddable link

In my example: <iframe allow="encrypted-media" allowfullscreen="" frameborder="0" gesture="media" height="315" scrolling="no" src="https://www.youtube.com/embed/87eG_zAbb9Y" width="560"></iframe>

Notice: in this case, the post preview will not work.

Hopefully, this will help you!

And now this webinar recording is available on InterSystems Developers YouTube Channel:

 

https://www.youtube.com/embed/LXTlYFTRZgk
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Please welcome!