Hello,
Two possible designs, from the top of my head, as a starting point.
If you want the checkbox to be checked only when editing a document {{checkbox checked='true'/}} should be enough.
If you want the checkbox to be checked also in view mode, you’ll need to:
- Generate a unique ID for each checkbox
- Save the checked checkbox IDs in an XObject in the document
In both cases, you’ll probably need some javascript to dynamically change the state of the document.
Note that you are not the first one to be interested in this feature (for instance, How to make dynamic checkbox for Xwiki?). So if you feel like it, you are encouraged to share the result as a contrib extension.
Hope that helps,
Manuel