Hi,
it would make users' workflow much quicker if there were a keyboard shortcut (such as "t" for example) which immediately opens the box to select a tag.
This feature would be even moe useful if users could select several tasks, press t on the keyboard and could then select a tag that is applied to all of the selected tasks at once.
A drag and drop feature with tags as a separate category on the left would also work, similar to how users can drag several tasks onto a certain context.