Tag messages from the keyboard, in both Zimbra clients:

• T and U come to the modern client: T opens the Tag dialog, U removes tags
• Y gives a message your first tag; each further press moves it to the next
• 1 to 9 add your first nine tags, one each; press one again to take it off
• In either client's tag dialog, 1 to 9 pick tags and Enter saves them

The keys work on the message you point at, or in classic on the selection.
They keep out of the way while you type, and of Zimbra's own shortcuts.
Switch them off under Keyboard in the ZTint popup.

Tinting is unchanged. Nothing you type is recorded, and ZTint sends nothing.