Here’s a quick walkthrough of how to set up an Automation using the Append last edited by script to automatically add a ‘last edited by’ note to the nominated topics created by the users at the set Trust Level(s). It’s really useful if you have any documentation or policy topics that you’d like to visibly show the last time they had any changes made to them and who by, and also uses the local dates functionality so each user can quickly see the edited date in their own timezone.
This is one that is relatively straightforward to set up. If you navigate to your Automation page and select the ‘Append last edited by’ script you’ll be presented with these options:
There’s only one trigger for this, ‘After post cook’, and you would then enter the categories and/or tags you’d like it to apply to, as well as a Trust Level for whose topics will be eligible for the note (a topic created by a user not included in that setting would not get the note attached, nor would one be added if an edit was made by someone who was).
There is also a handy way to add a category + all of its subcategories. If you start typing the category name of the parent category you should see an option similar to this appear:
Selecting that will populate the box with all of them, so no need to laboriously select them all individually if you have a lot of them. 
Once this is set, all topics in the categories or tags created by users at the set Trust Level will now have this note attached to them, which will be updated whenever they’re edited.
And that should be that. 
If you have any questions please ask them below or spin up a new support topic.
This also works really well in conjunction with the ‘Last checked by’ Automation to provide more comprehensive editing and review information. It works in a very similar way to this one, but you can read more about the details here - 'Append last checked by' Automation