To tag someone in a Coggle diagram, type @ followed by their name. A list of the people in the diagram who can be tagged will appear, and you can click or use the [tab] key to accept the suggestion.
You can use tagging in combination with checkbox task lists for assigning tasks in project plan diagrams, or to highlight people's responsibilities for particular areas of a shared mind map.
Each @NameTag is highlighted in a colour asigned to the person who's tagged, which is the same across all diagrams, so it's easy to see at a glance how who has been tagged in the diagram.
To tag someone, you must have first invited them to view or edit the diagram. If the name you use is unrecognised the tag will be grey.