How about introducing a new feature to insert a date or number as an attribute of tags? For instance, we may need to insert two dates, one for the due date and the other for the date I actually completed. In the case, we can insert e.g. @due(2018-07-01) @done(2018-06-30) to the task. Another example can be @priority(2). TaskPaper is supporting the feature and I found it is useful for many cases.
Yeah I like this idea, it could be a flexible way to setting priorities and for time-tracking.
Please like or comment if you like this feature request, and if enough people do we'll add it to the Trello roadmap