New install or re-install

If I get a new MacBook Pro to replace my 2019 one, do I need to reinstall Dorico on the new one or can I just transfer the existing install when my data is copied over? O???

It’s probably easiest to reinstall - I’ve read that using the Migration Assistant can be a bit messy. I’ve also read that it’s relatively easy to transfer your Dorico user data to the new machine via copying folders etc.

(There are more than a few threads about transferring Dorico to new machines that might be worthwhile taking a look at)

Migration Assistant is pretty good – it should copy over all your user settings, for example – But given the complexity, it’s best to reinstall using the Download Assistant, which will also deal with the licence authorization.

Should I also reinstall Download Assistant, or is it OK to copy that with Migration Assistant?

Yes, reinstall, because it puts various other component files in a variety of places.

Sorry to be so ignorant about such things. When I reinstall Download Assistant, how do I prove to it that I own a Dorico 6 License? Do I have some sort of Steinberg ID number or does my Dorico have a serial number? (I couldn’t find one.)

You have a Steinberg Account. The SDA connects to that account.
Perhaps this may help…

Steinberg Licensing: Steinberg Download Assistant guide – Steinberg Help Center