Black shapes and shared block templates

Couple of questions

1. When the mouse pointer hovers over a block type in a lesson - these black shapes appear (see image). What are they for?
2. Chat GPT tells me that block templates (shared with a team) will update automatically - but I can't get this to work. I create a shared block template. Insert it in another lesson. But when I modify the original the 'copy' doesn't update.

Thanks for the help