As in the attached examples (from Ligeti), sometimes you have to hide dynamics in some of the staves in a group.
Also, you may want to hide dynamics when they are implicit to human players, but not to virtual instruments (for example, when you want to slightly decrease, then increase volume before a new phrase).
As far as I understand, Dorico can’t hide hairpins, that have to be hidden via the Opacity color control. Dynamics marks (like pp, ff) can only be hidden in the Properties pane of the Engrave mode.
Hiding dynamics indications in Write mode is very important to me, since I use to insert this type of controls in the score for playback reasons. In exported parts, I can then make these indications visible again.
For the conductor score, I understand that I might use the CC lane instead of hidden dynamics indications (doing what I do in a sequencer). I’ve not tried this, but it seems less practical, when you can do the same in an easier way with traditional hairpins and dynamics abbreviations.