Message Header Toolbar Customize
Tag Toolbar/Tag Popup
This extension adds new toolbar and display the tags you have created as toggle buttons; the added toolbar is called "Tag Toolbar" and the space for showing tags is called "Tag Bar". You can attach/remove tags to/from the selected messages. The tag buttons' states are changed automatically, so you can easily know what tags are attached to the message. Moreover, you can filter the tags to be displayed by categorizing tags. You can create and change category from the listbox on Tag Bar.
Tag Toolbar is the same as original one. So, you can put other toolbar items on it. Tag Bar is the same as other toolbar items. So, you can move it to other toolbar. If you don't need Tag Toolbar, right click on the original toolbar and uncheck the "Tag Toolbar" menu.