very neat; I think I might get inspiration from this solution, apply it to the generic ViewTemplate but only look for [ ]- or [x]-prefixed lines.
In line with the conversation here, this seems to be easier to implement than modifying the parser in checklistdemo — a demo of the Checklist plugin for TiddlyWiki5 so that it generates the equivalent of <$draggable and <$droppable.
Well done!