Just to note, I’ve updated the OP with a table of all the existing Automations and their accompanying triggers. 
(I’m also hoping to add more guides too, as the one for ‘Add user to group…’ looks a bit lonely all by itself 
)
There are a couple more walkthroughs added for 'Append last edited by' Automation and 'Append last checked by' Automation. 
And a brand new script, User Group Membership through Badges. 
That one is pretty hot off the press so if you try it out, let us know how you get on.