Cancel only a part of syllables of the conversion result

[tats-u]

Mozc cancels all syllables by pressing BackSpace.
MS-IME can cancel only one by pressing Ctrl + BackSpace.

ime-cancel-syllable.mp4

ATOK cancels the current syllable and all following syllables by pressing BackSpace, but the cursor moves at the end of the current syllable (in Mozc all syllables are canceled and the cursor goes to the end of the entire input).

atok-backspace.mp4