@jsavage comments:

@cdent There is something counter-intuitive about the fact that the check boxes can be modified without editing the page. In some ways this is live editing without a save button. This makes me wonder if this is a one off or are there other controls that could be useful. Eg Drop down list for changing how a tiiddler behaves? Button for activating functionality in an SPA.

It is initially a bit odd isn't it? It's code that @FND wrote, as an extension to the Python Markdown library, borrowing the idea from Github where it is used to have task lists within issues. It makes it easy to have dynamic to do lists. If Javascript is present, clicking a box saves the tiddler with that box clicked in the Markdown.

It doesn't have to be a one off but there's nothing immediately planned. There a couple things in the works which kind of fit into this area:

• FND is working on some stuff that will allow something similar to Tiddlywiki macros in Markdown. Special markup in the tiddler will active javascript for just that tiddler. This is for his BFW project, but the same principles will be transferable to Tank.
• One the concepts for Tank is something called a widget, which will be a way to add custom commands on the right of every tiddler page in a tank that is configured. The details for that are very sketchy at this point.

There's a bit more about Widgets and Macros.