Splitting series of notes (hi-hats).

Hi, I’ve got a series of hi-hats that are all 1/4 in length. How do I cut them all into 1/8 notes using the split tool?
I tried selecting them all together and cutting in half with split, but it only splits one note at a time.

For now, I’m reducing the length by dragging from the right edge, and duplicating with alt+drag. It would be smoother if I could just split multiple notes at once.

The manual seems to indicate that multiple note split is possible. What am I doing wrong?
https://steinberg.help/cubase_pro_artist/v9/en/cubase_nuendo/topics/midi_editors/midi_editors_key_editor_note_events_splitting_c.html

Duplicate post.