Notehead without stem

How do I write notes without a stem!’ AND I want to do multifonics on clarinet is it possible to to show what holes to cover in Dorrico for the musician?
Sincerely Margaretha

Which of your questions is aimed at Cubase and which at Dorico?
Notes without a stem are usually either a half note or a full note, so I assume you mean something else. Kindly please elaborate.

In Dorico, select the note(s) and go into engrave mode. In the lower zone, in Properties, at the very end of the Notes and Rests section, you’ll find a switch for “Hide Stem”.

For Fingerings, I use the Legni Fonts.

They are on a pay-your-own-prize model and have worked very well for me. They offer fingerings for all common woodwinds, but not the German/Austrian variants of clarinets/oboes.

Once installed just create a text item and choose the right font. There is a manual included in how to enter the fingering.