App suggestion

Sibelius has an app that displays their notepad, allowing you to select note values on an iPad - which is faster than clicking on the screen.

I wish that Dorico had a similar app.

How does it work, if you don’t have to click (tap) on the screen?

There are plenty of numpad extensions for iPad, and they all work more or less well.
Beside that, there are two main options:

  1. the MetaGrid Pro app (one-time purchase) for which exist plenty of modules (such as my own for Sibelius, or the native one for Dorico, which comes bundled with the app).
  2. the StreamDeck app for iPadOS (subscription) for which you can purchase the Dorico module sold on Notation Central.

This assumes you do not want to buy the StreamDeck physical device and keep using your iPad (which was also my choice).

one hand uses iPad, the other hand plays the keyboard.

Oh, so you’re talking about using an iPad as an interface for the desktop.

As said, there are plenty of those that work with Dorico. I don’t see how it’s quicker than pressing the buttons on a real keyboard, though.

same hand for mouse and Komplete keyboard.

searched for notation central - found nothing

Notation Central