Then specifically for the Clavinova, here is a video explaining Single Finger Chords.

Clavinova Clinic - Understanding single fingered chords on Yamaha CVP digital pianos



Clavinova Clinic -Understanding multi-fingered chords on Yamaha CVP digital pianos



And here's a demonstration of playing Single Finger Chords on an older keyboard.

Play Piano Accompaniment With One Finger

I had noticed when watching one of the YouTube videos that on the Clavinova the choices for Single Finger, Fingered, and Multifingered Chords was on the same page as where you set the SPLIT POINT. So if your keyboard isn't automatically doing Single Finger Chords for you by 'default', maybe that is where to go and look.

A comment about using SINGLE FINGER CHORDS. If you are playing chords this way you can't use a LEFT HAND VOICE. Think about it. With a Left Hand Voice allocated the sound you get is generated from the actual notes you play. So if you are 'fingering' Am7 as A, C, E and G then that is what you hear for the Left Hand Voice. Sounds fine as those are the notes of the chord. But if you are using Single Finger Chords then your Am7 would be A, with Ab and G below it (or any black and white note below it), so your Left Hand Chord would sound those actual notes. The Ab would clash pretty horribly with the chord that was sounding for the Style!