Extented voicing on the bottom staff (as in the pic) on Dorico Elements

screenshot debussy
Hi to everyone,
I am trying to reproduce this voicing on Dorico Elements but I have no clue how to do it! Does anyone know how to do it? Many thanks in advance

Welcome to the forum @Sabrina_Parente !

It’s probably easiest to input the semiquavers/16ths that appear on the bottom staff on the top staff, then select those two notes and press M to cross them to the lower staff (they will still “belong” to the top staff and can be beamed to other notes on the top staff, but just appear on the bottom staff).

They’re in a down-stem voice on the top staff, so here’s information about inputting notes into different voices: