I can confirm that I've successfully executed block clips, ladder clips, and horizontal screen scrolls in both the US and JP Switch Online apps.

Tangentially related question... the Switch OS has a feature where you can double-tap the Home key to zoom in on a portion of the screen. This is pretty useful for checking whether you're aligned with the right pixel for screen scrolling. Would it be valid to use the Switch's screen zoom feature in a timed run? Or should it only be used for practice purposes?