I would love to be able to highlight a time span in the timeline and press a user-assignable keyboard shortcut to assign a tag.
When editing a tag, you would be able to configure the keyboard shortcut for it. For example, CTRL-1 could be assigned to Tag1, CTRL-2 to Tag2, and CTRL-3 to Tag3. Then instead of selecting a span in the timeline, right clicking, and clicking the tag, you could save time by just highlighting and hit CTRL-X to apply the appropriate tag.