Tags help you add additional context to your to-dos, across multiple lists. You can #tag your to-dos in the Web, Mac and Windows Apps. It will be making its way to our mobile apps (iPhone, iPad and Android) in a coming update, so be sure to tune in!
To tag a to-do, simply add a hashtag to a keyword, like you do on Facebook, Twitter or Instagram in the name of a to-do. Let’s say you’re planning a #vacation. Just add the word ‘#vacation’ to all of the relevant to-dos, in any of your lists.
Now here comes the magic part... with just one click of the #hashtag, we’ll find all of the relevant to-dos across your lists.