TinyMCE 6
Everyone is currently using ATTO editor. TinyMCE is the name of a popular text editor used on many websites. Moodle has for a long time had an older, outdated version, and perhaps you preferred that older ('legacy') version. This is a newer version which in a few years will become the main (default) editor for Moodle LMS, so you might like to try it out now.
Users on the site will be able to select it from Preferences > Editor preferences.
Find out more in the 4.1 TinyMCE editor documentation.
Indentation
You can indent an activity in Topics or Weekly format by selecting 'Move right' from the three dots next to an item.
Note that you can only move an item once to the right, and this indentation is reflected in the course index.
BigBlueButton
When you create your BigBlueButton (BBB) session, you will see a section Guest access. If you tick/check Allow guest access, then once you have saved the activity and return to its settings, you will be presented with a link and password that
you can share with the external speaker or attendee.